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. The issue of large photovoltage loss is a critical challenge for the development of p-i-n structured PVSCs, which bear great potential for flexible and multijunction solar cells. Here, we report an approach to modulate the defects and interfaces through LAIs for high-performance p-i-n structured PVSCs. By introducing the LAIs between the hole transport layer and perovskite layer in PVSCs, the non-radiative energy losses at both top and bottom interfaces of perovskite were simultaneously suppressed. More importantly, the LAIs have also inhibited the phase segregation on the perovskite surface, enabling a homogeneous surface properties. As a result, a high open-circuit voltage of 1.21 V and a champion PCE of over 22% were achieved, which is among the highest efficiencies reported for p-i-n structured PVSCs. Our work provides an effective strategy to control the optoelectronic properties of perovskite film. The non-radiative energy losses at both top and bottom interfaces of perovskite were simultaneously suppressed by introducing LAIs between the hole transport layer and perovskite layer. More importantly, the LAIs have also effectively inhibited the phase segregation on the perovskite surface, enabling homogeneous surface properties. As a result, a champion efficiency of over 22% was realized for p-i-n structured PVSCs, which is among the highest efficiencies reported for p-i-n structured PVSCs.