Built-In Electric Field-Promoted Perovskite p–n Heterojunction for Efficient and Selective CO2 Photocatalysis

Abstract Rapid charge carrier recombination and limited charge transport constrain the efficiency of semiconductor-based CO2 photoreduction. To address both limitations, p-type Cu2O was coupled with n-type Cs2AgBiBr6 (CABB) to construct a p–n heterojunction, in which the interfacial built-in electric field facilitates charge separation and directional carrier migration. Under simulated solar irradiation, 10 wt % Cu2O/CABB achieved a CO production rate of 27.51 μmol·g–1·h–1 and a CO selectivity of 83.07%. The CO production rate was 2.53 and 3.85 times the rates obtained over pristine Cu2O and CABB, respectively. The study demonstrates how a p–n heterojunction, together with the associated built-in electric field, enhances photogenerated carrier separation and photocatalytic CO2 reduction, while introducing a new approach to developing and optimizing photocatalytic materials with high selectivity.