Abstract
Two pairs of A-D-A molecules have been synthesized with fluorene and benzodithiophene as the central donor subunits and terminal BODIPY units, functionalized with either a 4-methylphenyl or 4-trifluoromethylphenyl group at the meso position. The effect of the para substituent of the meso phenyl group on the photophysical properties of these molecules is studied through steady state absorption and fluorescence spectroscopy as well as femtosecond transient absorption and time resolved fluorescence spectroscopy techniques. Applicability of these molecules as donors in solution processed solar cell active layers was investigated through time resolved microwave conductivity measurements on blends with PC60BM acceptor, which shows a varying yield of charge transfer with choice of substituent. Transient absorption spectroscopy is then employed to investigate the role of the 4-trifluoromethylphenyl group in altering the efficiency of charge transfer from these A-D-A molecules to PC60BM. The results show a consistent picture of picosecond charge transfer and a component of a few hundred ps geminate recombination that results in a small yield of long-lived free charges optimized for the methylphenyl derivatives.
Original language | American English |
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Article number | 108289 |
Number of pages | 9 |
Journal | Dyes and Pigments |
Volume | 177 |
DOIs | |
State | Published - 2020 |
Bibliographical note
Publisher Copyright:© 2020 Elsevier Ltd
NREL Publication Number
- NREL/JA-5900-75359
Keywords
- donor-acceptor
- solar-photochemistry
- time-resolved microwave conductivity
- transient absorption