A facile and broadly applicable CdBr2-passivating strategy for halide migration-inhibiting perovskite films and high-performance solar cells

Abstract

The defects including halide vacancies and uncoordinated Pb in perovskite films caused by the cracking of Pb–I bonds in the thermal annealing process are responsible for the degradation of the photovoltaic performance and long-term stability of perovskite solar cells (PSCs). Passivation of halide vacancies and uncoordinated Pb defects and construction of high quality perovskite films are vital to promote carrier lifetime and reduce non-radiative recombination losses. Herein, we develop a facile and broadly applicable surface passivation strategy for various compositional perovskite films, in which cadmium bromide (CdBr₂) is selected and adopted to passivate the halide vacancies and uncoordinated Pb defects of the perovskite films owing to the stronger bond energies of Cd–I and Pb–Br than that of Pb–I. CdBr₂ modification is found to be able to prolong carrier lifetime and decrease defect amount together with improving film quality of the typical compositional perovskites i.e. MAPbI₃, Cs_0.15FA_0.85PbI₃ and CsPbI₂Br, as evidenced by spectral and photoelectrochemical measurements. As a result, the photovoltaic performance and ambient, photo and thermal stability of perovskite devices are greatly promoted, with a high efficiency of 16.05% achieved by the CdBr₂-modified PSCs with the architecture of ITO/SnO₂/MAPbI₃/carbon, exceeding the previous highest PCE record for carbon-based MAPbI₃ PSCs.