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 exceeded 13% at present. Especially, the benzothidiazole-T4 families of polymers, such as PffBT4T-2OD, have attracted tremendous research interest in academic communities since they can be processed into highly efficient fullerene/polymer solar cells with power conversions up to 10%. Herein, we reported 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. The PBT4T-Cl-based devices also showed less additive dependency than the control devices did (PffBT4T-2OD-based). 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, all of which supported the PCE enhancement of chlorine-substituted benzothiadiazole-T4 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.

Chlorinated π-conjugated polymer with efficiency over 11% and enhanced stability in organic solar cells

255th National Meeting (2018)

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