Enhancing the efficiency and stability of inverted binary organic solar cells through hydroxylated perylene diimide derivative cathode interlayers

Cathode interlayers (CILs) are crucial components in organic solar cells (OSCs), and the quest for outstanding overall performance in these materials remains a central research focus. In this study, we introduced a series of cost-effective perylene diimide derivatives (PDI derivatives) featuring hydroxylated side chains, namely PDI-Br-0O, PDI-Br-1O, and PDI-Br-3O. These hydroxylated CILs exhibit wider optical bandgaps and possess low-lying molecular orbitals, which can contribute to efficient photon utilization and enhanced charge transport within OSCs. As a result, the inverted cell with PDI-Br-3O achieved an outstanding power conversion efficiency (PCE) of 18.1%, representing one of the highest values recorded in inverted binary OSCs. Furthermore, these hydroxylated PDI derivatives enabled OSCs to consistently achieve PCEs exceeding 17%, even with a 30 nm-thick PDI-Br-3O layer. Of particular significance, the operational stability of these solar cells was notably improved with increasing the CIL thickness in the range from 5 nm to 30 nm. Remarkably, even after continuous illumination for 550 hours, the device equipped with a 30 nm-thick PDI-Br-3O CIL still retained 83% of its original efficiency. This study presents a promising design strategy for CILs offering exceptional comprehensive performance, providing a significant impetus for the potential commercialization of OSCs. We report a series of hydroxylated PDI derivatives as CILs with exceptional comprehensive performance. After continuous illumination, the extrapolated T80 lifetime for the device with a 30 nm-thick PDI-Br-3O is estimated to be 3995 h.