Functionalized BODIPYs as tailor‐made and universal interlayers for efficient and stable organic and perovskite solar cells

Solar cells based on metal halide perovskite and polymer donor:nonfullerene acceptor blend absorbers have recently witnessed a significant rise in their photovoltaic performance. However, they still suffer from some instability issues originating from the inferior interface quality and poor nanomorphology of the absorber layer. In this work, a series of functionalized boron-dipyrromethene, BODIPY, molecules are introduced as ultrathin interlayers at the absorber/electron transport layer interface. This study indicates that BODIPY compounds with a high molecular dipole moment can enhance the device performance mainly due to better interface energy level alignment. They also induce passivation of defect traps and improvement in the charge transport properties of the absorber layer coated on top of them. Among the various compounds used, amino-functionalized BODIPY, owing to the synergetic effect of the abovementioned factors, enables the highest power conversion efficiency in organic (15.69%) as well as in perovskite solar cells (20.12%). Amino-functionalized BODIPY also demonstrates an enhanced stability under continuous illumination (in nitrogen) without and with heating (at 65 °C) for 1000 h. These results pave the way for the implementation of molecules with tailor-made functionalities in high efficiency and stable solution-based photovoltaic devices of the future.