Lifetimes Kinetics for Ester and Non-Ester ATZ Acceptor Coupled with 2,2'-Bithiophene Donor Conjugated Copolymers Using Time-Resolved Spectroscopy

Photoinduced charge transfer dynamics are critical for evaluating the suitability of organic materials in solar cell applications. In this study, I employed femtosecond-to-microsecond time-resolved spectroscopy to investigate the excited-state kinetics of two donor–acceptor (D–A) conjugated copolymers: ATZ-BT (P1) and ATZE-BT (P2). These copolymers share the same core structure but differ in their side chains, with P2 containing an ester-functionalized alkyl group. These results reveal that the non-ester polymer P1 facilitates efficient charge transfer, making it a promising candidate for photovoltaic applications. Conversely, the ester-substituted P2 shows significantly reduced charge transfer efficiency, rendering it unsuitable for solar energy harvesting. This conclusion is supported by both steady-state and transient spectroscopic measurements. To the best of my knowledge, this is the first report to characterize the photophysics of these specific azo-thiazole based copolymers using a comprehensive time-resolved approach from femtoseconds to microseconds.