Efficient and thermally stable all-polymer solar cells based on a fluorinated wide-bandgap polymer donor with high crystallinity

All-polymer solar cells (all-PSCs) based on an n-type polymer as an acceptor material and a p-type polymer as a donor material have attracted great attention due to their excellent device stability. However, a systematic study of the thermal stability of all-PSCs has not been reported to date. Herein, we developed a highly efficient and thermally stable all-PSCs based on a fluorinated wide-bandgap polymer donor (PFBZ) and a narrow-bandgap polymer acceptor (N2200). The PFBZ:N2200 pair exhibited complementary absorption spectra, matched energy levels, and good blend morphology. As a result, PFBZ:N2200-based devices after thermal annealing at 150 °C for 15 min achieved a high power conversion efficiency (PCE) of 8.1% with a high open-circuit voltage of 0.90 V, a short-circuit current density of 13.5 mA cm^-2, a fill factor of 67.0%, as well as a low energy loss of 0.56 eV. The efficiency of 8.1% is one of the highest values reported for the additive-free all-PSCs. When the thermal annealing time was extended to 180 min or the temperature was increased to 250 °C, the all-PSCs retained a high PCE of over 7%. These results indicate that the PFBZ:N2200-based all-PSCs with high efficiency and excellent thermal stability are promising candidates for the practical applications of OSCs.