In situ NbOx as an efficient interfacial layer on an SnO2 electron-transport layer for high-performance and stable flexible perovskite solar cells

Abstract

Long-term environmental and mechanical stability issues of flexible perovskite solar cells (F-PSCs) hinder their commercialization. Interface defects affect the performance of F-PSCs, especially their stability and power conversion efficiency (PCE), which is derived from carrier recombination and mechanical stability between adjacent layers. Herein, we report an NbO_x passivation layer in situ formed at the interface between the SnO₂ electron transport layer (ETL) and perovskite layer with the microisland bulge nanostructures. This approach reduces nonradiative recombination loss and optimizes band alignment. As a result, the open-circuit voltage (V_oc) from 1.13 to 1.17 V, leading to a photoelectric conversion efficiency of 23.64% on the glass substrate (active area of 0.09 cm²). Additionally, the PSCs demonstrated exceptional stability, retaining over 80% of their initial efficiencies after 2000 hours of exposure to ambient atmosphere without encapsulation. Furthermore, the solution-processed and low-temperature available interfacial layer was applied to F-PSCs, achieving a PCE of 21.86%. The flexible device retained over 74.94% of its initial PCE after 10 000 bending cycles at a radius of 5 mm.