Feng He1

1, Southern University of Science and Technology, Shenzhen, Guangdong, China

With the development of material engineering, interface modification, and advanced device processing in past decades, the power conversion efficiency (PCE) of the state-of-the-art PSCs has already reached 12% at present. we designed a novel chlorinated polymer donor PBT4T-Cl, and the PSCs using PBT4T-Cl showed a high PCE of 11.18%, which is the highest PCE of chlorinated polymer-based PSCs and is also one of the highest PCEs of FBT-based PSCs reported to date. The results demonstrated chlorine substitution of the thiophene moiety could tune-finely the HOMO energy level of the corresponding polymer as well as the charge carrier mobility and the morphologies of the blend film, eventually improving its photovoltaic properties as a donor without requiring thermal annealing. The PBT4T-Cl-based devices also showed less additive dependency than the control devices did (non-Cl-based polymer). Analysis on the GIWAXS illustrated the strong crystallinity from the blend film, and AFM and TEM measurements both revealed an optimized morphology of the spin-coated PBT4T-Cl/PC71BM film without thermal annealing, all of which supported the PCE enhancement of chlorine-substituted polymer, and chlorine atoms attached to a suitable backbone would obviously promote the performance of polymer solar cells. Moreover, the chlorinated polymer-based PSCs exhibited favorable stability in the lifetime test compared with non-chlorinated analogs. Therefore, chlorination of the polymer donor is a feasible strategy to simultaneously increase the performance and stability of PSCs, eventually promoting the commercialization of PSCs.