Modulation of Defects and Interfaces through Alkylammonium Interlayer for Efficient Inverted Perovskite Solar Cells

Perovskite solar cells (PVSCs) with p-i-n configuration bear great potential for flexible photovoltaics and all perovskite or Si-perovskite multijunction solar cells because of their low-temperature processability. Nevertheless, the state-of-the-art efficiencies of p-i-n structured PVSCs suffer from non-ideal interfacial recombination and charge-extraction losses. To address these challenges, we employed a large alkylammonium interlayer (LAI) to reduce the energy loss occurred between transport layers and perovskite. The use of LAIs, in contrast with the reported bottom or top surface passivation strategies, can simultaneously suppress the non-radiative energy losses at both top and bottom interfaces of perovskite. As a result, the reduced surface recombination velocity (SRV) and trap state density (N_t) enable a substantially improved photovoltage from 1.12 to 1.21 V for the PVSCs with an optical band gap (E_g) of 1.59 eV, leading to a champion power conversion efficiency (PCE) over 22%, which is among the highest efficiencies reported for inverted PVSCs.