Electrolyte Immersion Increases Photoconductivity in a Model Polymer Photocathode

Journal Article · Mon Jul 28 04:00:00 EDT 2025 · ACS Energy Letters

DOI:https://doi.org/10.1021/acsenergylett.5c01809· OSTI ID:2587056

Kopcha, William ^[1]; Mohapatra, Aiswarya ^[2]; Davis, Casey ^[2]; Thurston, Jonathon ^[2]; Suh, Eui Hyun ^[3]; Dong, Bo ^[4]; Brown, Megan ^[5]; Basu, Aniruddha ^[2]; Chen, Zejie ^[6]; Ardo, Shane ^[6]; Risko, Chad ^[5]; Lian, Tianquan ^[4]; Ratcliff, Erin ^[3]; Barlow, Stephen ^[1]; Marder, Seth ^[1]; Toney, Michael ^[2]; Gish, Melissa ^[1]; Ferguson, Andrew ^[1]; Reid, Obadiah ^[1]

---

1. National Renewable Energy Lab., Golden, CO (United States)
2. University of Colorado Boulder
3. Georgia Institute of Technology
4. Emory University
5. University of Kentucky
6. University of California, Irvine

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.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 2587056
• Report Number(s): NREL/JA-5900-93523
• Journal Information: ACS Energy Letters, Journal Name: ACS Energy Letters Journal Issue: 8 Vol. 10
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
microwave conductivity
photoelectrochemical
photomodulation
polaron
polymer
time-resolved microwave conductivity
transient absorption