2017 Fiscal Year Research-status Report
Eco-friendly water-based microemulsions for large-scale and low-cost organic photovoltaics windows
| Project/Area Number |
17K14549
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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, 大学院情報理工学研究科, 助教 (10731713)
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| Project Period (FY) |
2017-04-01 – 2019-03-31
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| Keywords | Organic Solar Cells / Aqueous dispersions / Functional surfactant / Donor:acceptor domains / Green process / Conjugated Nanoparticles / Light manipulation / Self-assembly |
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| Outline of Annual Research Achievements |
Hydrophobic conjugated segments (PCPDTBT) were linked to hydrophilic P4VP blocks of various lengths to produce block copolymers (BCP) for surfactant-free water dispersions of electrically active nanoparticles fabrication. We studied the influence of the P4VP chain length on the BCP:fullerene acceptor domains size, nanoparticle size, hole conductivity and power conversion efficiency (PCE) in polymer solar cells (PSCs). When short P4VP chains are employed, we achieved PCEs of 2.5% and 10-fold increases in hole conductivity with respect to PSCs produced using hazardous chlorinated solvents. Compared to conventional devices, the nanoparticle-based PSCs exhibit a 20% higher short-circuit current density (Jsc) of 11.5 mA/cm2. Transient absorption measurements suggest that this is due to the formation of smaller donor and acceptor domains confined in the nanoparticle which enhance the photoinduced charge generation efficiency.
Additionally, we investigated an alternative green deposition process for PSC active layers (push-coating) which considerably reduces the amount of used hazardous solvents and produced inverted PSCs with PCEs up to 5.2%.
Lastly, we used self-assembled polymer thin films to fabricate nano- and micro-domes employed to increase light in-coupling into the PSC active layer. With these optical coatings, Jsc was increased by 7.9% under normal light incidence and, unliked uncoated devices, the PSCs worked efficiently even when light was tilted up to 30 degrees. These coatings are thus ideal for practical implementation of PSCs as photovoltaic window technology.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Due to issues with the materials stability in air, the synthesis of copolymer based on higher performance conjugated polymers (e.g., PTB7) is more difficult than expected. Consequently, we were not yet able to produce nanoparticle solar cells with PCEs over 5%. Nonetheless, we achieved that objective using the push-coating process.
We were also able to fabricate thiophene-based polyelectrolye materials which we will test as water-soluble electrodes or active material for PSCs in FY2018.
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| Strategy for Future Research Activity |
In FY2018, the following experiments are scheduled:
1. Explore the use of water-soluble fullerenes (e.g., C60-PEG) to facilitate the nanoparticle formation and continue synthesizing block copolymers based on higher performance materials to achieve water-processed PSCs with PCEs over 5%. We will also apply the thiophene-based polyelectrolytes synthesized in FY2017 as solution-processed cathode material and/or water-soluble electron donor in the PSC active layers.
2. We will continue exploring the push-coating method as this green process can be readily employed with most conjugated polymer-based active layers. We will adapt it to produce nanostructured interfaces inside the device architecture (e.g., electron-only layer/active layer interface) to further increase the light in-coupling to the PSC active layer and increase the PSC device performances.
3. We will fabricate transparent or semi-transparent electrodes using either solution processes (e.g., with silver nanowires coated with electron or hole transporting materials) or thermal evaporation processes (e.g., composites of thin metal layers and metal oxide layers) for large-scale ITO-free photovoltaic window fabrication.
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Research Products
(9 results)
