Enhanced optical absorption and efficient cascade electron extraction based on energy band alignment double absorbers perovskite solar cells

An original CsPbI x Br 3-x /FAPbI y Br 3-y absorber is designed to form C 60 /CsPbI x Br 3-x /FAPbI y Br 3-y multi-heterojunction perovskite solar cells with optimized energy band alignment by precisely adjusting I:Br proportion in these two perovskite absorbers. The introduction of CsPbI x Br 3-x can not only improve the optical response, but also act as an electron transport conductor to form a band-matched cascade electron extractor with C 60 . Optimized optical response and well-matched energy levels greatly enhance carrier transport and reduce carrier recombination, affording a high PCE of 17.48%, with high V OC , J SC , FF and excellent device stability simultaneously. Our results shed light on the importance of the interface engineering on the electron excitation and extraction of perovskite layers and describe an innovative approach to further boost the efficiency of perovskite solar cells.