2014 Fiscal Year Annual Research Report
Innovative architectures to simultaneously enhance organic photovoltaic device stability and efficiency
| Project/Area Number |
26889029
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
VOHRA Varun 電気通信大学, 情報理工学(系)研究科, 助教 (10731713)
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| Project Period (FY) |
2014-08-29 – 2016-03-31
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| Keywords | 有機太陽電池 |
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| Outline of Annual Research Achievements |
During this first year, a focus was given to increasing the efficiency of both graded bilayers and bulk heterojunctions taking into account the effect of the crystallinity of the polymer over the device performances.
In collaboration with RIKEN, very high efficiency devices (up to 10%) were achieved with a new polymer (PNTz4T) which displays high crystallinity. We investigated the crystallinity and the crystal orientation in regular and inverted bulk heterojunction devices and related these to the device performances.
On the other hand, the crystallinity of P3HT was also increased by using solvent additives in graded bilayer devices. The devices prepared with higher boiling point solvent additives (compared to chlorobenzene) display an enhancement of the efficiency. More specifically, solid trichlorobenzene can be used as a crystallizing agent and the device efficiency can be increased from 2.5% to 3.3%. The reasons for this increase in device efficiency are still under investigation.
In parallel, a focus was given to the stamping and lamination processes. To obtain adequate lamination/transfer conditions, it is necessary to take into account the interfacial forces in the various device architectures. Using this approach, we were not only able to fabricate devices using a golf leaves as top electrodes (much cheaper than vacuum deposition) but also we were able to deposit P3HT:PCBM bilayers on PDMS. The transfer process of the P3HT:PCBM bilayer still needs to be optimized but this will be part of the research conducted during the second year.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
The initial research project was based on fabricating devices directly in the laboratory at the university of electro-communications. However, due to lack of research funds, the installation of an operating system for vacuum evaporation took longer than expected. As a result, in order to prepare devices, we had to rely on the collaboration of other groups (mainly at RIKEN, Saitama Prefecture and JAIST, Ishikawa Prefecture).
However, the devices fabricated are very promising and the results are probably better than expected initially.
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| Strategy for Future Research Activity |
During the second year, a focus will be given to the deposition of the active layer on the PDMS stamps to increase the quality of this active layer and to the transfer of this layer to a working device architecture.
The results during the first year have been very promising. By using plasma treatment of the PDMS stamp, the surface tension of the stamp was modified to be able to deposit either water based or organic solvent based solutions by spin-coating. However, by using plasma treatment the transfer process becomes more difficult and we will therefore investigate other forms of thin layer deposition on PDMS.
On one side, we may use solvent additives (surfactants) to deposit either the P3HT layer directly on PDMS or use a sacrificial layer for easier transfer.
Once this is achieved, we will investigate the transfer process on either ITO/ZnO substrate or PCBM covered substrates and find the optimum conditions for both pressure and temperature.
The final step of the second year will be to fabricate working devices and investigate the thickness dependence of the active layer over the device performances. If the devices perform correctly, higher efficiency materials will be used to fabricate high efficiency inverted bilayer solar cells.
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Research Products
(1 results)
