Introducing thiazole units into small-molecule acceptors for efficient non-fullerene organic solar cells

The end-group modification engineering has been widely applied in non-fullerene acceptors (NFAs) to achieve high-performance organic solar cells (OSCs). Herein, we designed and synthesized a series of small-molecule acceptors (SMAs), namely ODTz-gamma, ODTz-m, DTTz-gamma and DTTz-m, which containing the electron-withdrawing thiazole units on the end groups at different position. These SMAs not only exhibited strong and broad ab-sorption region from 500 nm to 900 nm, identical band gaps, but also the similar energy levels, indicating the position of thiazole units have trivial effect on their absorbance and energy levels. OSCs were fabricated by integrating an electron-donating polymer PBDB-T with these resultant electron-accepting materials. Devices based on ODTz-gamma exhibited an obviously higher power conversion efficiency over 12.0%, which outperformed those of obtained from devices based on other SMAs. Further characterization of the devices revealed that introducing the thiazole units into the gamma position of end groups can enhance the charge transport mobility, suppress recombination, and improve the blend film morphology.

Automated summary

The end-group modification engineering has been applied in non-fullerene acceptors to improve the performance of organic solar cells. In this study, a series of small-molecule acceptors with different positions of electron-withdrawing thiazole units were designed and synthesized. These acceptors exhibited strong absorption and similar energy levels, leading to higher power conversion efficiency. Further analysis showed that introducing thiazole units into the gamma position of end groups can enhance charge transport, suppress recombination, and improve film morphology.