Ester-functionalized chlorothiophene incorporated PM6 based copolymers for ternary organic solar cells

초록

Ternary organic solar cells (OSCs) offer an effective strategy to simultaneously improve open circuit voltage (Voc), short circuit current density (Jsc) and fill factor (FF) by fine-tuning the optoelectronic landscape of the active layer. Here, we report a newly designed wide bandgap donor polymer, poly [(2,6-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)-benzo [1,2-b:4,5-b']dithiophene))-alt-(ethyl 3-chloro-2,5-thiophenediyl-4-carboxylate)] (PMFE), and a series of PMFE based copolymers synthesized through copolymerization with PM6. When introduced as a third component into PM6:Y6 blend, the PMFE based copolymers enable systematic modulation of the donor energy levels and optical absorption without compromising the nanoscale morphology of the host blend. Ternary devices incorporating an optimized amount of 2.5 wt% of the PMFE based copolymers exhibit simultaneous enhancements in Voc, FF, leading to a maximum power conversion efficiency of 16.6%. The improved device performance is accompanied by improved external quantum efficiency responses across the visible spectrum and reduced recombination, as evidenced by light intensity dependent measurements. These results demonstrate that rationally designed wide bandgap copolymer donors can serve as effective third components for enhancing the photovoltaic performance of high efficiency OSCs.

키워드