Upon Dyenamo's high-purity perovskite precursor salts
5 September 2019 / Henrik Pettersson
Researchers and companies that develop chemistry-based solar cells such as perovskite cells are always looking for the “best chemicals”. The definition often becomes the material that gives the highest device efficiency. Interestingly enough, laboratories often end up with different winning material compositions. The source of this may be caused by manufacturing methods or laboratory environment, but material impurities may also play a role. It is interesting to note that many laboratories use a specific perovskite precursor material without knowing the reasons for the high device performance. When a new batch does not deliver the same device performance as the last one, there is often no follow-up on what caused the difference, apart from contacting the material supplier…
Dyenamo’s philosophy is that material purity is the way to control the perovskite solar cells. Pure materials have turned out to be crucial for device reproducibility and often beneficial for device performance. In addition, a highly pure perovskite precursor material opens for realizing the optimum composition for a given end-user via deliberate introduction of additives. As a consequence of this, Dyenamo has introduced three grades of MAI, FAI, MABr, FaBr and MaCl, specified as >99 %, >99.99 % (grade 4N) and >99.999 % (grade 5N), respectively. In addition, all products can be manufactured upon specification. As an example of this, we have introduced a special grade of MAI (DN-P02P), with an increased amount of phosphite, as this has turned out to be beneficial for the device performance in certain laboratories.
By using the materials specified as >99 % purity, small batch to batch variations caused by trace impurities may occur. The risk for such trace impurities affecting the solar cell performance and/or device reproducibility is strongly reduced by using grade 4N and removed by using 5N. Consequently, by using the 5N material, a laboratory can be confident that the same material is obtained in every delivery. In order to secure that all the products can be stored outside dry environment, we have added an additional hermetically sealed water-barrier to the products.
Another year has come to an end and I maintain the tradition of summarizing the past year from a Dyenamo perspective, starting by thanking all our customers, project partners and colleagues. I also want to address my gratitude to our distributors around the world. Dyenamo is still a small company and to efficiently reach out on a global market without all of you would not be possible.
Since the start in 2011, Dyenamo´s ambition has been to offer the latest findings in chemistry-based solar energy conversion. Originally, this was material-components for dye-sensitized solar cells. This approach has been maintained for the rapid development in the field of perovskite solar cells. During 2018, our internal development activities for perovskite solar cells have focused on highest purity of the perovskite-salts on kg-batch levels. The results are very satisfactory, and we enter 2019 with great self-confidence and expectations for the perovskite-business. I also want to highlight the carbon paste DN-CP01 (see previous blogpost from 2018) that has opened new prerequisites for perovskite research and development.
I also want to highlight the fact that we receive an increasing number of requests for materials on demand, not limited to solar cell applications. Repeatedly, we have managed to deliver complicated materials towards a given specification, confirming the capability of the Dyenamo synthetical team.
The H2020 project ESPResSo, which started in April 2018 is Dyenamo´s first participation in an EU-funded project. After eight months, I can already conclude that it is a very valuable and rewarding experience to collaborate with leading European research groups and companies to develop improved perovskite solar cells.
Apart from materials, the activities on characterization equipment has been intense. The potentiostat DN-AE05 is a cost-efficient and highly accurate IV-measurement solution designed for small solar cells (<1 cm2) and low-power (indoor ambient light) applications. As the product is based upon a computer-controlled potentiostat, it can also be used for various low-current (<15 mA) electrochemical applications. In combination with the power meter DN-AE06, we now offer a kit for IV-measurements at various light-conditions, ranging from low-power indoor to solar outdoor measurements. I am also pleased to conclude that our dye-sensitized solar cell toolbox (DN-AE01) and our photo-induced absorption spectroscopy (PIA) setup (DN-AE02) are becoming standard tools in the field. Moreover, our IPCE equipment (DN-AE03) has been upgraded for more efficient use for perovskite and other PV technologies.
With regards to laboratory manufacturing equipment, we offer a broad set of products, such as equipment for device encapsulation, screen printing, electrode sintering, spin-coating, glass-cutting, hole-drilling and spray pyrolysis. I especially want to highlight the glass cutter (made by our partner Elixir Technologies) that has simplified the daily work for many PV laboratories.
Once again, many thanks for a great year. I am looking forward to hearing from you during 2019.
Why Dyenamo's carbon paste DN-CP01 can influence the entire perovskite field
24 April 2018 / Henrik Pettersson
Academic activities on perovskite solar cells are so far mainly performance-driven. However, this is about to change as it is becoming more and more demanding to further increase cell-efficiency record-values. Moreover, the record cell-efficiencies are already so high that it has been proven that the technology must be treated seriously also from an industrialization point of view, especially when taking the low-cost features into consideration. Many research groups are thus broadening and re-focusing their perovskite activities towards accelerated testing, understanding of degradation mechanisms, and investigation of novel device concepts. Other applications than solar cells such as LEDs and x-ray detections are also intensively explored.
The industrial module-developers obviously have another approach where they need to define the specifications of their targeted market, and realize competitive device performance combined with long product life using reliable, cost-efficient scalable process methods and materials. One branch of the existing perovskite module-industry is heading towards tandem devices where the perovskite device is placed on top of e.g. a silicon device. The second branch is heading towards independent perovskite modules. In both cases, a central piece of the puzzle is to use a suitable cell concept. Several ongoing module-industrialization efforts for the above-mentioned second branch are going in the direction where a carbon electrode is used as the hole-accepting electrode in a monolithic geometry, i.e. a triple-structure consisting of TiO2, spacer and carbon. These layers are collectively sintered whereupon the perovskite solution is introduced into the porous structure. After crystallization, i.e. formation of the perovskite structure in the pores, the device is ready. Since serial-connections can be integrated in the structure, the transfer from cell to module is straightforward. This concept takes away the need for a hole conductor and a metal back-contact opening for a cost-efficient device. It is a beautiful solution where the drawbacks to date are performance, the need for a spacer layer and a limitation to glass-substrates due to the required sintering temperature. This analysis directed us to develop a low-temperature curing carbon paste that could be applied directly to a perovskite layer, i.e. the paste is applied after crystallization without an intermediate spacer or hole conductor. As this now has been realized with the carbon paste DN-CP01, I want to highlight the following consequences:
1. Cell efficiencies above 15 % have already been reached by our partner KTH in Stockholm (publication in progress) verifying the functionality of the paste in perovskite solar cells
2. The paste opens for a planar cell structure (i.e. no TiO2) consisting merely of a perovskite layer and carbon on a conducting substrate. Crystallization in a planar structure is more controllable than in a porous structure.
3. Serial-connections can be made with the carbon layer enabling an efficient transfer from cell to module. Alternatively, current collectors can be applied on top of the carbon layer opening for larges cells.
4. Flexible substrates can be used as the curing temperature is low and the carbon layer can be bent.
With the paste DN-CP01, Dyenamo provides a key prerequisite for both academia and industry to investigate, develop and commercialize one of the simplest imaginable solar cells, on rigid or flexible substrates.
To find out more about our carbon paste DN-CP01, or send a quotation request, click here.
ESPResSo, an ambitious EU funded collaboration to make Perovskite solar cells a market reality
19 April 2018 / Henrik Pettersson
The first of April was the start of the three-year project ESPResSo (Efficient Structures and Processes for Reliable Perovskite Solar Modules). I am very proud that Dyenamo is a part of this world-leading perovskite solar cell consortium, which has been granted over five million Euro by the European Union. Apart from Dyenamo, the members of the consortium are coordinator IMEC (Belgium), EPFL (Switzerland), University of Rome, CNR and CSGI (Italy), Fraunhofer (Germany), University of Cyprus, Dycotec and M-Solv (UK), Onyx (Spain), Corning (France) and Saule (Poland).
The ESPResSo team covers the full spectrum from fundamental studies to industrialization via e.g. studies of sustainability issues and development of materials, process technology and prototypes. Dyenamo's tasks are naturally material-oriented.
The ESPResSo project is the first one for Dyenamo in Horizon 2020. It places us exactly where we aim to be, i.e. in the centre of the world-leading perovskite solar cell activities!
Another year has come to an end and it is time to thank all our customers and colleagues for an intense, challenging, successful and rewarding 2017.
Dyenamo started out as a company providing state-of-the-art material-components for chemistry-based solar energy technologies. Over the years, we have slowly but steadily increased our activities and today, manufacturing and characterization equipment, training and consulting services are as natural parts of our business as the material-components. This has all been realized without abandoning our model based on sustainable growth.
My personal Dyenamo 2017 highlight was the "DSSC strikes back" conference in Uppsala. We took a big step outside our comfort zone and managed to, all on our own, organize a very successful event. I am also pleased to see that our patent portfolio for the next generation DSSC materials/concepts (one-electron redox mediators such as copper and cobalt, and so-called zombie devices and their key components) are developing according to plan. Together with our increased material-component production capacity, we have a strong package. Our pieces of characterization equipment (e.g. toolbox, PEC-holder, PIA) have been implemented as standard tools in several laboratories. Additional equipment will be launched in 2018, keep your eyes open!
Our collaboration with Elixir Technologies in Bangalore was taken to the next level as we were appointed exclusive distributor for their manufacturing equipment for dye-sensitized and perovskite solar cells outside India. Consequently, we now offer a broad set of products, such as equipment for device encapsulation, screen printing, electrode sintering, spin coating, glass cutting, hole drilling and spray pyrolysis.
I am proud of the fact that Dyenamo is part of the ESPRESSO consortium, which has been granted a three-year EU-funded Horizon 2020 project on perovskite solar cells. In collaboration with coordinating IMEC (Belgium), EPFL (Switzerland), University of Rome, CNR and CSGI (Italy), Fraunhofer (Germany), University of Cyprus, Dycotec and M-Solv (UK), Onyx (Spain), Corning (France) and Saule (Poland), we collectively take on the challenge of bringing the technology to the next maturity phase.
Once again, many thanks for a great year. I am looking forward to hearing from you during 2018.
Impressions from the Dyenamo Conference DSSC Strikes Back, Uppsala October 2017
23 October 2017 / Henrik Pettersson & Anders Hagfeldt
The Dyenamo DSSC conference "DSSC Strikes Back" was triggered by the fact that we sensed an upcoming trend for dye-sensitized solar cells (DSSC), driven by exploiting unique features of the DSSC technology, mainly esthetic properties and great functionality at low-light conditions, i.e. IoT-conditions. In addition, DSSC researchers and companies had no active forum to meet, exchange ideas and discuss.
The event was kicked off by a Training & Coaching day where 16 participants met to learn from and discuss with the Dyenamo founders and staff. This was followed by a welcome reception where approximately 60 people showed up. Already during this day, we felt a strong curiosity regarding the present status of the DSSC field in combination with a very positive attitude and good mood.
The oral presentations of the following two-day conference, with 115 participants from 18 countries, started with Michael Grätzel. He directly showed that this was no walk down DSSC memory lane but an opening of a new intensified DSSC era, with novel materials and concepts. He was followed by industrial talks from H.glass in Switzerland and Dongjin Semichem in South Korea. They both demonstrated that there are strong industrial DSSC activities and many exiting DSSC BIPV installations. This, and the ongoing DSSC industrialization for low-power applications, were confirmed by several industrial speakers from Exeger (Sweden), Aisin Seiki/Toyota (Japan), Everlight (Taiwan), 3GSolar (Israel) and Songtextile (Japan). Most of these companies also displayed DSSC products/protoypes in the DSSC module showroom. In addition, the impressive DSSC-covered building in Shanghai presented by Prof. Hujiang Shen from Shanghai Institute of Ceramics, Chinese Academy of Sciences took most people by great surprise. With regards to surprise, the presentation and technology demonstration from Ingmar Brüder of trinamiX, a subsidiary of BASF, lifted many eyebrows. A unique feature, focus-induced photoresponse, first discovered in DSSC devices, makes it possible to e.g. measure distances in a completely new way. It was a pleasure to take part of Ingmar's fascinating story and his charismatic personality.
From an academic perspective, the conference gave an excellent summary of the state-of-the-art in terms of materials and devices. With the introduction of new redox couples such as Co- and Cu-complexes there is now a clear direction how to improve the record efficiencies. The low driving force for dye regeneration allows open circuit photovoltages above 1.1 V as described by Michael Grätzel and Marina Freitag. Development of new organic and porphyrine dyes, as presented by for example Elena Galoppini and Hwan Kyu Kim, in combination with the new redox systems indicate the possibilities to beat the present certified record efficiency. High efficiencies need to be obtained together with excellent stability and Frédéric Sauvage gave a very interesting talk on fundamental studies of degradation mechanisms. Several talks also drew attention to the importance of the different interfaces in the devices. For example, Sabina Scarabino and Jacqueline Cole discussed the development of SECM and in situ neutron reflectivity to investigate the interfacial properties. Water-based electrolytes, dyes with different colors, p-type DSSCs, etc, were other topics, which show the beautiful chemistry and the versatile materials platform of DSSC.
Collectively, the industrial and academic speakers, poster presenters and participants demonstrated a vibrant community and clearly proved that DSSC is strong both scientifically and from an industrial viewpoint. From an organizational point of view, we are very proud of how the Dyenamo team managed to host the event, despite the fact that this was out of our comfort zone. Positive and engaged participants made it very easy to organize things. Thank you to everyone involved!
We are already looking forward to our next DSSC conference, scheduled for 2018.
Simple additive in cobalt electrolyte improves the efficiency of dye-sensitized solar cells by 2% units
06 March 2017 / Gerrit Boschloo
Hybrid electrolytes, which contain more than one redox couple, have been investigated in dye-sensitized solar cells for a long time. For instance, Bignozzi and co-workers combined ferrocene and phenothiazine, which show fast electron transfer processes, with cobalt(II/III) trisbipyridine, which has rather slow kinetics ( J. Am. Chem. Soc. 2006, 128, 9996-9997). Their results were not impressive, but they made a good point: the kinetics of cobalt mediators are rather slow. Later, Kloo and co-workers added TEMPO to cobalt electrolyte, which led to a nice improvement in efficiency, from 7.1% without to 8.4% with TEMPO additive (Cong et al., ChemSusChem 2015, 8, 264 – 268). The stability of this system was rather poor.
In recent research led in my group we found that the addition of tris(p-anisyl)amine (TPAA) to a standard cobalt-based electrolyte led to a marked improvement of performance of the dye-sensitized solar cell from 8.4% to 10.5% in a co-sensitized system (Hao et al., Nature Commun. 7 (2016) 13934 | DOI: 10.1038/ncomms13934 ). We found that both voltage and current improve, by as much as 100 mV and 3 mA cm-2, respectively. This is due to the much faster dye regeneration step by the TPAA, on a nanosecond timescale. Electron recombination to the oxidized dye is effectively prevented. We demonstrated that the function of dye regeneration and charge transport is effectively separated in the hybrid electrolyte: regeneration is done by TPAA, while Co(bpy)32+/3+ takes care of charge transport in the electrolyte. Finally, we could also demonstrate good stability of the devices.
I believe that this finding can lead to new records in dye-sensitized solar cell performance. Moreover, TPAA can in principle be added to any electrolyte system. TPAA is available from Dyenamo as product DN-X04.
Impressions from the AP-HOPV conference in Yokohama
09 February 2017 / Henrik Pettersson
For the first time, the HOPV conference was organized in Asia, more precisely at the harbor of Yokohama in Japan. It was a very positive experience and excellent facilities in a beautiful location. The timing of the conference was somewhat unfortunate since it collided with the Chinese New Year vacation period, which likely reduced the number of participants. The number of European participants was low, likely due to the upcoming HOPV conference in Lausanne in May this year.
The conference lectures were very perovskite-dominated. Things are still moving fast in the field. According to me, there was an increasing number of presented activities on modules and stability. However, I was actually hoping that there would be even more ones since this to me represents a technology maturity step. As in earlier DSSC development, the perovskite field also faces a situation where stable cell efficiencies and module efficiencies are significantly lower than champion devices. This is caused by modified chemistry and/or process methods. Regarding DSSC, I sense an upcoming activity trend after two years where the technology was “shaded” by the perovskite boom. As previously mentioned in the Dyenamo blog, we foresee increased activities on Cu-based DSSC electrolytes, both liquid and solid-state ones (“zombie” devices). This was supported by conference presentations and the high number of questions in relation to them.
Once again, it is time to summarize a Dyenamo year. As last year, I wish to start by thanking all Dyenamo's customers and colleagues for an intense and successful 2016. The most representative Dyenamo word for 2016 is expansion; applicable for sales, number of customers, number of employees, size of R&D projects, number of products, batch sizes etc. This has all been realized without abandoning our model based on sustainable growth. Here are a few of my personal Dyenamo highlights from 2016:
we passed the threshold of having 100 material products
the Dyenamo team hosted an Indonesian scientific delegation for a tailor-made training in Stockholm
we have demonstrated that organic hole-conductors can be both highly efficient and affordable
the Dyenamo toolbox is being established as a standard characterization tool for DSSC research
our agreements with strategic partners in Asia
our patent-pending PEC holder opens new possibilities for photo-electrochemical research
Taking into account the latest results from research on perovskite and dye-sensitized solar cells, I am convinced that 2017 will be another thrilling year. New redox couples, such as Cu-based ones, have given the whole DSSC field a new boost. Moreover, the fact that stability has now been proven for perovskite solar cells automatically takes the technology to the next maturity level. It is with great pride I conclude that Dyenamo materials have been involved in both advancements. In 2017, I am confident that we will experience a significant increase of activities focusing on perovskite modules and alternative DSSC chemistry based on organic dyes in combination with new redox systems and hole-transport materials. Moreover, I can promise that Dyenamo will continue to be very active in offering the best materials for these (and other) activities.
Once again, many thanks for a great year. I am looking forward to hearing from you during 2017.
For a long period of time, spiro-OMeTAD has been the obvious choice of molecular hole-conductor for perovskite solar cells and solid-state DSSCs. This era may now have come to an end, since a large number of novel hole-conductors appear at an impressive rate. Many of these are used to obtain very high device efficiencies demonstrating that many different hole-conducting materials can be used to match the spiro efficiencies. Looking further down the road, the winning hole-conductors will be the ones that, in addition to high device-performance, are low in production cost and that provide highly stable devices. Dyenamo’s choice of the first runner-up is the so-called X60 (DN-X02) hole-conductor, developed by our colleagues at KTH in Stockholm. This material has been implemented in top-efficiency perovskite devices (around 20%) by the groups of Profs. Anders Hagfeldt and Michael Grätzel at EPFL (DOI: 10.1039/C6EE00056H). In addition, the X60 material is attractive from a large-scale production point of view and can thus already from the start be offered at very competitive prices (DN-X02).
I would like to thank all of Dyenamo's customers and colleagues for an intense and successful 2015. We have continued to develop the company according to our model based on the foundation of sustainable growth. During the year, we have expanded our production and development facilities and expanded the organization by several recruitments. In addition, we have been engaged in three significant R&D projects. We have followed our previous path by continuing to launch many new products for chemistry-based solar technologies, mainly solar fuels, perovskite solar cells and dye-sensitized solar cells. I am pleased with the increased interest for materials on demand, where we custom-synthesize material-components. Despite the fact that several orders have been very demanding, I am proud to conclude that we have without exception successfully delivered the ordered materials. The Dyenamo team is prepared and committed to continue to take on new challenges and carry on the same dy(e)namic path in 2016.
21 December 2015 / Henrik Pettersson & Anders Hagfeldt
The authors of this blog share a great interest in sports and we often have discussions regarding similarities between solar cell research and team-based sports. Both share the challenge to make strong individuals to work as a team. In addition, solar cell research and sports share the same passion for world-records. Solar cell efficiency world-records attract attention, career possibilities and opens for funding, whereas sport-records attract fame and sponsor deals. From an industrialization point of view, solar world-records probably have a minor impact. However, for showing the potential of technologies, reaching out to the public and obtain interest from society, they are very important.
It is now three years ago that the Dyenamo web-site was created. Today more than 100 products for dye-sensitized solar cells, perovskite solar cells and solar fuels have been launched – a record in itself. More importantly, Dyenamo materials are currently used in world record devices for all three technologies.
i) Dye-sensitized solar cells:
Our organic dye LEG4 (D35cpdt, DN-F05) was used to obtain the reported efficiency values exceeding 14%, see K. Kakiage, Y. Aoyama, T. Yano, K. Oya, J. Fujisawa and M. Hanaya, Chem. Commun., 2015, DOI: 10.1039/C5CC06759F. For the record efficiency, Co-phenanthroline complexes were used as redox mediator, see Dyenamo products DN-C07 and DN-C08.
ii) Perovskite solar cells:
Three weeks ago EPFL established a new world record efficiency for Perovskite Solar Cells, with a certified conversion efficiency of 21.02%. The efficiency was certified on December 1 at the laboratories of Newport Corporation in Bozeman, Montana. The new conversion efficiency eclipses the previous record of 20.1%.
In their record cell EPFL used the Dyenamo Co-dopant DN-P04 (FK209).
iii) Solar fuels:
This is a more diversified research field and record efficiencies are not as well defined as in the solar cell community. Dyenamo specializes in molecular solar fuel components and devices. State-of-the art efficiencies are based on Ru-complex light absorbers and catalysts immobilized on mesoscopic TiO2 electrodes for oxygen evolution, and the P1 organic dye, Co-complex catalysts and NiO electrodes for hydrogen evolution. Such devices are for example described in J. Am. Chem. Soc., DOI: 10.1021/jacs.5b04856. All these components can be ordered from Dyenamo.
Behind each of these records lies a tremendous parameter-testing work by the device-manufacturers. Different materials are tested against each other in a massive optimization process. It has actually not been Dyenamo´s ambition to provide world-record materials. However, it is a very rewarding fact to conclude that Dyenamo manages to launch the right materials and quality to be included in the record devices.
Last week, Bill Gates released the document “Energy Innovation – Why we need it and how to get there”. In this report, he focuses on solar energy and highlights the following three technologies as particularly interesting; i) Solar chemical, ii) Flow batteries and iii) Solar paint. Translating these terms into the Dyenamo vocabulary, Solar chemicals means Solar fuel and Solar paint means Dye-sensitized solar cells/Perovskite solar cells. The document is obviously very encouraging for everybody that has been involved in this technology development; scientists, companies, Universities, research institutes, funding agencies, investors etc. We should all be very honored by and proud of this endorsement. However, more importantly we should also be even more motivated to proceed on our path. Collectively, we can make a difference!
One of the commercially most interesting aspects of the DSSC technology has always been the fact that it outperforms other technologies at fluorescent light, especially at light-intensities below 250 Lux. This is also a somewhat confusing part of the PV world since there is no established standard for measuring power output, i.e. different lamps and spectra are used by different producers and for different technologies. One should therefore always be aware of this when comparing values.
Personally, I made my first low-power DSSC device in 1994 when working for Professor Michael Grätzel at EPFL. The devices were made for fluorescent light and intensities between 50 and 250 Lux. By using a classical sandwich device construction, we obtained power densities that by far exceeded those from amorphous silicon devices. The transfer from hand-made to machine-made devices resulted in so-called monolithic one-substrate devices, also with performance advantage in relation to amorphous silicon devices. I considered DSSC on glass-substrates being technically mature for commercialization for low-power applications in 2003. However, it took several years before DSSC low-power commercialization took place. My personal opinion is that this was caused by the hard cost-competition from low-power amorphous silicon cells. Moreover, the improvement of battery technology was fast and electronic equipment got more complicated requiring more power. A few years later, however, commercialization of flexible low-power DSSC on plastic substrates was initiated by the company G24Power in Wales. A large-volume production line was built and products were, and still are, brought to market.
The world of internet-of-things opens for a massive amount of novel applications for solar devices powering sensors. For such applications, DSSC has an additional competing technology in GaAs devices. It is interesting to see how different companies on their web-sites claim to have the world-leading low-power solar technology. This is probably related to the previously-mentioned lack of standardization. No matter what technology and producer is world-leading, it is of major importance that the performance of low-power DSSC is significantly improved in order to remain a competitive low-power technology. In order to do this, it is time to exchange the traditional DSSC-chemistry consisting of Ru-dyes and iodide/triiodide-based electrolytes. Dyenamo has focused hard on developing the next chemistry generation for low-power DSSC. By using our organic dyes and cobalt-based electrolytes, we have reached power densities above 20 µW/cm2 at 250 Lux fluorescent light. This is, to my knowledge, a top-value for low-power PV technologies. At Dyenamo, we are confident that chemistry based upon one-electron redox mediators, such as cobalt, is the way to out-perform all other technologies at low-power conditions, and that further development in this direction will result in continuous performance-improvements.
A breakthrough for solid-state dye-sensitized solar cells
5 June 2015 / Anders Hagfeldt & Gerrit Boschloo
Referee comments are often read in an emotional state between hope and despair. But in rare occasions one gets happily surprised as in reading the title of this blog as a comment from one of the referees to our work on Cu-complexes as a novel hole transporting material for solid-state dye-sensitized solar cells (ss-DSSC).
Ss-DSSCs have been developed for more than 20 years with a starting point of Tennakone and coworkers already in 1988 using CuSCN as an inorganic hole conductor. The most studied hole transporting material (HTM) is spiro-OMeTAD, first published by EPFL in 1998, with a top efficiency of about 7% for ss-DSSC. This organic compound is also the standard HTM for perovskite solar cells. It is, however, expensive. The current commercial price of high purity spiro-OMeTAD is for example over ten times that of gold. While increased demand would undoubtedly lower this cost dramatically in any large-scale commercial endeavor, it is likely to remain expensive due to the synthetic methods and high purity needed for photovoltaic applications. Moreover, the electronic properties of spiro-OMeTAD such as work function and hole mobility may be limiting for development of different light absorber materials and contacts.
In our work on alternative redox couples for liquid type DSSC we followed the promising works by Hattori and Peng Wang and their co-workers on Copper-phenanthroline complexes. With this redox system Wang’s group published a top efficiency of about 7%. The post-doc Marina Freitag in our Uppsala-group could conclude that Cu-phenanthroline is indeed a very strong contender to the established redox systems for DSSC based on iodide/tri-iodide or cobalt complexes. But her and our co-workers’ studies came also with a big surprise! Having left some of the liquid sandwich solar cells with a Cu-phenanthroline electrolyte for some months with an unsuccessful sealing, the solvent of the electrolyte had evaporated and the cells had dried out. For somewhat unclear reasons the cells were anyway tested and - lo and behold – the efficiencies of the dried cells were even higher compared to the initial liquid cells. Marina quickly coined the name “Zombie cells” for these dry and supposed-to-be dead cells. With the Dyenamo organic LEG4 dye we reached the highest power conversion efficiency up to date for organic ss-DSSC of more than 8% efficiency, which was compared to spiro-OMeTAD with efficiencies between 5 and 6%.
These materials give the availability of modifications to tune redox potentials and to optimize hole transport. We believe that these preliminary results open up new directions for integration of this new class of HTMs not only to ss-DSSCs or perovskite solar cells, but also in other areas of organic electronics, where the use of HTMs is essential. The initial results are now published in Energy & Environmental Science, 2015, DOI: 10.1039/C5EE01204J.
Over my years in the dye-sensitized solar cell (DSSC) field, I have in several projects had the oppurtunity to work together with Andreas Hinsch from Fraunhofer ISE. As he now enters the field of perovskite solar cells, I want to make you aware of why we should pay attention to his points of view.
Around 20 years ago, Andreas came up with the idea of encapsulating DSSC modules with so-called glass-frits. It did not receive that much attention since the field was focused on using polymeric encapsulation solutions. In 1997-1999, Andreas and myself collaborated in a project on DSSCs for indoor applications. We then received several remarks that this was not of commercial interest since amorphous silcon had already done what there was to do. After this, Andreas focused on see-through modules, i.e. using the esthetic advantages of DSSC. This work was somewhat questioned since the efficiencies were low. The ongoing industrialization of the DSSC technology involves the technology directions Andreas worked on, i.e. indoor DSSC devices and see-through esthetic devices sealed with glass-frits. We should thus all learn from the past and listen carefully when Andreas presents his vision on how to manufature perovskite modules.
Being at a conference in Rome is a cultural experience. When walking through the beautiful historical city centre on the way to the conference, it is hard to comprehend that I am on my way to a working day. I shared my time at the conference between the Dyenamo stand, the lectures and the poster sessions. The lectures were as expected dominated by work on Perovskite solar cells. It struck me and others that HOPV this year took a turn towards being more physics- than chemistry-oriented. The progress on the Perovskite cells is fast and impressive, now with efficiencies exceeding 20 %. Nevertheless, I would have liked to hear more on stability, module technology and upscaling. Hopefully, this will be on the menu next year at the HOPV16 in Swansea. In my opinion, the big news in the DSSC field were i) the impressive phasade demonstrator at the Expo 2015 in Milan shown by Michael Grätzel, ii) the nice module work from Aldo di Carlo and colleagues at Dyepower, and iii) the innovatove work on Cu-based hole conductors from Marina Freitag and colleagues at Uppsala University. The latter two were unfortunately hidden in the poster session but deserve much more attention. I also noticed a number of lectures on solar fuel, which is another field that Dyenamo is involved in.
The exhibition was slightly hidden and comprised nine exhibitors, less than last year at HOPV14 in Lausanne. For me, it was very stimulating to meet customers, colleagues, old and new friends. HOPV has always been a friendly place with a great atmosphere. I have enjoyed reading all the contributions to the Dyenamo letter-box. The winner will be announced within shortly. Thank you to all participants for helping us launching the right products.
I greatly appreciated all the endorsements for the Dyenamo business model based on the foundation of sustainable growth. By maintaining the company ownership, we can build a dy(e)namic company attractive to work with that offers cutting edge high-value materials and solutions to our customers.
United Nations proclaimed 2015 as the International Year of Light and Light-based Technologies (IYL 2015), www.light2015.org. This is in recognition of the importance of light-based technologies in the promotion of sustainable development providing solutions to global challenges in health, energy, agriculture, education, etc.
Light propagates throughout our lives, cultures and history. It is an essential component in describing Creation, irrespective of our views in science or religion. The understanding of the nature of light encompasses a fascinating history of science. Is it a wave or a particle? For Newton it was a stream of corpuscles and for Huygens a wave vibrating in ether. The courageous act of Einstein to embrace the curve-fitting constant from Planck’s work on black body radiation as a physical entity gave us the concept of photons and the birth of quantum mechanics.
Light is also technology. Electromagnetic radiation connects us around earth with the use of mobile phones, Skype and social media. Photonic technologies share a global market of some hundred billion Euros. Works by Rembrandt and Turner as well as modern laser shows are some of the examples we can appreciate in understanding the impact of light in culture. The fascination with and the excitement of seeing a rainbow and the wonder of watching the Northern lights evoke the emotional side of our relationship to light. As for my own favorite I will pick the magic light of a Swedish summer night.
Light is intimately connected to chemistry. Defining chemistry as “the science where things can be made that were never made before”, we directly relate to synthesis and together with light we have of course the photosynthesis. And a growing scientific quest is to make Artificial Photosynthesis. I am just back at EPFL from a highly successful conference in Uppsala, “1st International Solar Fuels Conference – ISF-1”. The solar fuel community is growing quickly and the conference hosted an impressive number of about 500 participants. Dyenamo’s role in this field is to support the research groups with standard materials, specific requests of molecular light absorbers and catalysts, research tools, etc. It will be two exciting years to come to see where the field stands at the next meeting, ISF-2, in San Diego, 2017.
Light and chemistry is the bread and butter for Dyenamo. The international Year of Light is a year to celebrate for our company and I am certain that we will see new concepts, exciting discoveries and world record efficiencies in our core activities of photochemical solar cells and solar fuels.
I would like to thank all of Dyenamo's customers and colleagues for a stimulating and successful 2014. It has been an intense year; we have launched many new products, including analytical pieces of equipment, for solar fuels, perovskite solar cells and dye-sensitized solar cells. In addition, we have expanded our production facilities, expanded the organisation by recruitments, obtained the Ingemar Croon award and two significant R&D projects.
In parallel to this, it is fascinating to see the career development of the Dyenamo founders; Anders Hagfeldt becoming Professor at EPFL, Lars Kloo becoming Secretary General for Science and Engineering at the Swedish Research Council, Licheng Sun being awarded with the Arhenius medal and Gerrit Boschloo taking the overall responsibility for the DSSC/ Perovskite research at Uppsala University. I am pleased to conclude that they all remain very active and engaged in the Dyenamo development. Together with our coworkers, we are prepared to continue on the same successful Dyenamo path in 2015.
“Meten is weten” is a well-known Dutch phrase, meaning approximately “to measure is to know”. During my research career, that started in the Netherlands before moving to Sweden, I have done a lot of measurements on dye-sensitized solar cells. But quite often these did not give me the answers I was looking for. The main question was: How does the dye-sensitized solar cell work in detail? I therefore set out to develop new measurement techniques, inspired by Galileo Galilei:
“Measure what can be measured and make measurable what cannot be measured.” Galileo Galilei (1564-1642)
In our research team, we developed methods to follow the photoinjected electrons in the mesoporous TiO2 on their way to the substrate, or to the redox electrolyte when recombination occurs. We also found ways to see the spectrum of oxidized dye molecules and electrons in the mesoporous TiO2 electrode under solar illumination conditions. These methods gave us a lot of know-how, and I am sure that advanced measurement techniques are essential for better understanding of the DSSC and further development of DSSC materials.
Dyenamo now gives access to two advanced techniques developed in our solar cell research.
First, the Dyenamo toolbox for electron transport time / lifetime and charge extraction measurements. The toolbox measurements are very quick to perform and easy to analyze, so that more cells can be tested and significant trends can be found. Similar information can be found using electrochemical impedance spectroscopy (EIS), but EIS measurements are time consuming and data analysis is tedious.
Second, the Dyenamo photoinduced absorption (PIA) spectroscopy system. PIA is performed under conditions that are similar to solar illumination, using low intensity on/off excitation, rather than an intense laser pulses. At a fraction of the cost of a nanosecond-transient absorption spectrometer, the Dyenamo PIA system offers an easy way to assess the electron injection of dyes into TiO2, and the regeneration of these dyes by redox mediators.
On the long-term stability of Co-based electrolytes
18 November 2013 / Lars Kloo
Since the combination of a bulky, organic sensitizing dye and a one-electron, and cobalt-based, redox system in 2010 (Hagfeldt, Sun et al., JACS, 132, 2010, 16714), one route to higher conversion efficiencies has been highlighted (Grätzel et al., Science, 334, 2011, 629). However, the new strategy based on transition metal complexes is not without obstacles to overcome. Already from the start the long-term stability has been questioned for this type of systems, in particular focusing on the stability of the cobalt complexes. Going towards multidentate ligands has been one promising approach (Bach, Long et al., JACS, 134, 2012, 16646). Modifying the electrolyte solvent system is another (Kloo, Achari et al, PCCP, 15, 2013, 17419). By optimization of the electrolyte composition recent and soon-to-be-published studies look highly promising also for volatile, organic solvents, showing excellent stability over 1000 hours under 1 Sun light-soaking conditions at 60 degrees. Thus, to my opinion, one-electron systems have a bright future for high-performing DSSC devices. The future will tell if the cobalt-systems will prevail or if they will be replaced by alternatives.
I’m on my way home from a 10 days visit to the lab of Prof. Nam-Gyu Park at SKKU, Korea. Besides the interesting research discussions and some insights in Korean culture I have also given classes for a PhD course in photoelectrochemistry. The idea was to go through introductory lectures of scientific topics that are needed in the interdisciplinary area of photolectrochemistry and in particular dye-sensitized solar cells (DSSC); semiconductor physics, electrochemistry, photochemistry, electron transfer theory, photocatalysis, to mention some. The interesting experience with the course was to mix lectures of these well-established subjects with the teaching of how DSSC works. It felt exciting, and a bit nostalgic, to tell how our community developed the diffusion model, trapping/detrapping, design rules for push-pull dyes, tool-box measurement techniques, module designs, plastic DSSC, etc. The research of DSSC is rich with science, people and stories.
Also today, the research of mesoscopic solar cells is more intense and dynamic than ever. This is definitely clear after having visited one of the pioneering labs for the last year's development of perovskite solar cells. The unexpected use of this material started as a curiosity with the work of Prof. Tom Miyasaka and with the replacement of the iodide-based electrolyte with a solid-state hole conductor the breakthrough happened last year with the works of Park/Grätzel and Snaith/Miyasaka. Now the record efficiencies are above 15% and with such a short time of development we can only expect more. There are also intriguing fundamentals questions to be studied and some answers are now starting to be published (see for example the reports by the groups of Snaith and Sum. Our own record efficiencies are also promising reaching above 13%. For practical applications there are more to be done, in particular to check stability and up-scaling and process development. Perovskite solar cells have all the potential to challenge the conventional photovoltaic technologies but to be something more than its contenders in the thin film PV category, I think it's important to, for example, keep a solution-based processing, avoiding high investment costs of vacuum deposition technologies as well as allowing for large volume continuous production methods.
The industrial interest is still mainly focused on DSSC. The up-scaling has been done and longterm stability has been proven, glass facade walls are constructed, etc. In my view the future for DSSC is to niche for designer applications. The possibility to make solar cells in any color and with any transparency makes the technology ideal for consumer electronic products as well as building integration. DSSC got the look! (paraphrasing some Swedish music).
I'm privileged and happy to have been part of setting up Dyenamo with dear friends and colleagues having known each other for 15-20 years. It's an exciting adventure and journey to see how Dyenamo can develop to be a platform for commercial interactions with researchers and entrepreneurs for hopefully another 20 years of intriguing scientific activities and discoveries as well as industrial exploration.
I would like to share some of my thoughts regarding organic DSC dyes. A few years ago, I admit having considered them interesting from a fundamental rather than an applied point of view. Clearly, they were attractive from a feedstock and an upscaling perspective. However, I did not think that they would challenge the conventional Ru-dyes such as N719, C101, and C106. This has turned out to be a huge mis-judgement.
The turning point was when my co-workers at Uppsala university and KTH showed that organic dyes efficiently block recombination for one-electron redox mediators opening for high efficiencies. This finding was quickly picked up by EPFL leading to new DSC efficiency records. However, this was just the beginning. Thereafter, it has been shown by us and others that organic dyes, especially our own D35 (DN-F04) can lead to exceptionally stable DSC devices in combination with iodide/triiodide ionic liquid electrolytes, also at high temperatures. In addition, the possibility to make well-performing dyes in different colors make them even more attractive.
To sum up, I now believe that organic DSC dyes are here to stay. Dyenamo is working hard to deliver the best possible ones, today and in the future.
I am thrilled to write the first lines in the Dyenamo blog. The Dyenamo team has had the idea to initiate a blog for a while and now it is happening. We will use this medium to share the experiences and updates of the Dyenamo co-founders, i.e. Gerrit Boschloo, Anders Hagfeldt, Lars Kloo, Henrik Pettersson and Licheng Sun. The discussion topics will be interesting novelties in the DSC and solar fuel field, comments regarding publications, trends, conferences etc. We will continuously publish a new blog-post, which collectively should give a broad perspective on dye-sensitized solar cells and solar fuels.
It is now many years since I started to work on DSCs. I have spent one year at Ekologisk Energi AB, four years at EPFL, 15 years at Swerea IVF AB and two with Dyenamo. Over the years, I have seen DSC materials and scientists come and go. However, some of us remain like my Dyenamo-colleagues Anders Hagfeldt and Gerrit Boschloo, the N3 and the N719 dyes, the Pt counter electrodes, the FTO glass, the, MPN-based electrolytes. It is a privilege to have followed the DSC technology from childhood towards industrialization. Clearly, the latter is challenging for all of us. To my opinion, it is in the interest of all DSC scientists that the ongoing efforts to commercialize DSC modules are successful. Dyenamo is our contribution to support this; a team of experienced DSC people offering our services and materials.
I wish you all welcome to the Dyenamo blog and hope that you will find it to be interesting and stimulating reading.