Significant Efficiency and Stability Enhancement of Flexible Perovskite Solar Cells Combining with Multifunctional Effects of a Natural Spice

The numerous defect-induced non-radiative recombination losses and residual stress in the preparation of perovskite film greatly hinder the further improvement of the efficiency and stability of flexible perovskite solar cells (PSCs). Here, a natural spice 7-amino-4-(trifluoromethyl)-2-benzopyrone (ATB) containing amino (-NH2), carbonyl (-C=O), and trifluoromethyl (-CF3) functional groups is introduced into the perovskite precursor solution, thereby preparing high-quality perovskite film with low defect density. It is revealed that the utilization of ATB is beneficial to comprehensively passivate the defects and release the residual stress of perovskite film through the synergistic effect of functional groups, thereby improving the crystallinity and enhancing the carrier lifetime of perovskite film. Moreover, the introduction of ATB contributes to an improved energy levels alignment between the perovskite and adjacent layers, which facilitates fast carrier transport and suppresses the recombination loss in the flexible PSCs. Combined with the multifunctional effects of ATB, the target flexible and rigid PSCs with ATB modification yield remarkable photoelectric conversion efficiency (PCE) of 21.08% and 23.79%, respectively. More importantly, the ATB-modified flexible device exhibits outstanding stability and retains 87.3% and 91.6% of the original efficiency after aging for 3000 h at 50 +/- 5 relative humidity and 5000 bending cycles, respectively.