Enhanced UV-light stability of planar heterojunction perovskite solar cells with caesium bromide interface modification

Interfacial engineering has been shown to play a vital role in boosting the performance of perovskite solar cells in the past few years. Here we demonstrate that caesium bromide (CsBr), as an interfacial modifier between the electron collection layer and the CH 3 NH 3 PbI 3− x Cl x absorber layer, can effectively enhance the stability of planar heterojunction devices under ultra violet (UV) light soaking. Additionally, the device performance is improved due to the alleviated defects at the perovskite-titania heterojunction and enhanced electron extraction. CsBr interface modification simultaneously enhances the device power conversion efficiency and improves the device resilience to UV irradiation.