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DOE OSTI · 2587056

Electrolyte Immersion Increases Photoconductivity in a Model Polymer Photocathode

Kopcha, William [National Renewable Energy Lab., Golden, CO (United States)]·Mohapatra, Aiswarya [University of Colorado Boulder]·Davis, Casey [University of Colorado Boulder]·Thurston, Jonathon [University of Colorado Boulder]·Suh, Eui Hyun [Georgia Institute of Technology]·Dong, Bo [Emory University]·Brown, Megan [University of Kentucky]·Basu, Aniruddha [University of Colorado Boulder]·Chen, Zejie [University of California, Irvine]·Ardo, Shane [University of California, Irvine]·Risko, Chad [University of Kentucky]·Lian, Tianquan [Emory University]·Ratcliff, Erin [Georgia Institute of Technology]·Barlow, Stephen [National Renewable Energy Lab., Golden, CO (United States)]·Marder, Seth [National Renewable Energy Lab., Golden, CO (United States)]·Toney, Michael [University of Colorado Boulder]·Gish, Melissa [National Renewable Energy Lab., Golden, CO (United States)]·Ferguson, Andrew [National Renewable Energy Lab., Golden, CO (United States)] (ORCID:0000000325441753)·Reid, Obadiah [National Renewable Energy Lab., Golden, CO (United States)]
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Abstract

Immersing polymer solar cells in aqueous electrolyte for photoelectrochemical (PEC) hydrogen production is likely to cause photophysical changes that could present both challenges and opportunities for engineering functional and durable devices. Herein we study the bulk heterojunction blend poly(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)-alt-(2-(((2-ethylhexyl)oxy)carbonyl)-3-fluorothieno[3,4-b]thiophene-4,6-diyl):poly(N,N'-di(2-octyldodecyl)naphthalene-1,8:4,5-bis(dicarboximide)-2,6-diyl)-alt-(2,2-bithiophene-5,5'-diyl) (PTB7-Th:N2200) excited-state dynamics in electrolyte from femtosecond to millisecond time scales using pump-probe microwave conductivity and absorption spectroscopy. While the blend swells very little, electrolyte exposure increases the microwave-frequency mobility and possibly the yield of photogenerated charges while also decreasing crystallinity. These results indicate an enhancement in key performance metrics, implying that any limitations on the performance of PEC test devices do not arise from active layer-electrolyte interactions. For the PTB7-Th:N2200 blend or similar photocathode systems, our results indicate that improving the interfacial kinetics and/or the carrier lifetime should be prioritized, not protecting the active layer from the electrolyte. Since this observation may not be universal to all polymer systems, future research should focus on identifying their limiting photophysical processes. electrolyte.

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14 SOLAR ENERGYmicrowave conductivityphotoelectrochemicalphotomodulationpolaronpolymertime-resolved microwave conductivitytransient absorption

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Kopcha, William [National Renewable Energy Lab., Golden, CO (United States)], Mohapatra, Aiswarya [University of Colorado Boulder], Davis, Casey [University of Colorado Boulder], Thurston, Jonathon [University of Colorado Boulder], Suh, Eui Hyun [Georgia Institute of Technology], Dong, Bo [Emory University], Brown, Megan [University of Kentucky], Basu, Aniruddha [University of Colorado Boulder], Chen, Zejie [University of California, Irvine], Ardo, Shane [University of California, Irvine], Risko, Chad [University of Kentucky], Lian, Tianquan [Emory University], Ratcliff, Erin [Georgia Institute of Technology], Barlow, Stephen [National Renewable Energy Lab., Golden, CO (United States)], Marder, Seth [National Renewable Energy Lab., Golden, CO (United States)], Toney, Michael [University of Colorado Boulder], Gish, Melissa [National Renewable Energy Lab., Golden, CO (United States)], Ferguson, Andrew [National Renewable Energy Lab., Golden, CO (United States)] (ORCID:0000000325441753), Reid, Obadiah [National Renewable Energy Lab., Golden, CO (United States)]. 2025-07-28. Electrolyte Immersion Increases Photoconductivity in a Model Polymer Photocathode. https://doi.org/10.1021/acsenergylett.5c01809

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