Molecular design enabled reduction of interface trap density affords highly efficient and stable perovskite solar cells with over 83% fill factor

Abstract Advancing perovskite solar cell (PVSC) technologies toward its theoretical power conversion efficiency (PCE) and optimum stability requires stringent control over interfacial trap densities in the devices. By introducing a new macromolecular interlayer material of PPDIN6 at the PCBM/Ag interface for planar p-i-n PVSCs, we succeeded in significantly reducing the trap density, thereby facilitating electron extraction and suppressing electron recombination at the interface. Consequently, a PCE of 20.43% was achieved with a record fill factor of 83.4%, which is one of the highest values for planar p-i-n PVSCs. Moreover, the amine groups in PPDIN6 could neutralize the migrating iodide ions and thus inhibit the formation of the insulating Ag–I bonds on the surface of the Ag electrode. As a result, we realized long-term stability for PPDIN6 based PVSCs, which maintained 85% of their initial performance after continuous operation at their maximum power point for 200 h under 1-sun illumination in air with a relative humidity of 30–50%.