Reversible oxygen-induced <i>p</i>-doping of mixed-cation halide perovskites

To fully unlock the potential of metal halide perovskites (MHPs) for use in optoelectronic devices, a comprehensive understanding their electronic properties is strong demand but presently lacking. This photoelectron spectroscopy study reveals that thin films three important mixed-cation/mixed-halide MHPs behave like intrinsic semiconductors with very low defect concentration. The Fermi level position bandgap can be varied by almost 1 eV choosing substrates appropriate work function samples were handled under inert conditions. Upon oxygen exposure, two organic/inorganic-cation become strongly p-doped due to diffusion into bulk, process reversible when storing ultrahigh vacuum. In contrast, all-inorganic CsPbI1.8Br1.2 exhibits no property changes upon exposure. Nonetheless, found effectively remove (light-induced) lead-related surface states CsPbI1.8Br1.2.