fig5

Figure 5. Interfacial doping for perovskite homojunctions. Electric field distribution as a function of depth within p-i-n PSCs (A) without and (B) with GABr treatment through cross-sectional KPFM. Reproduced from Chen et al.^[46]. (C) A method for controlled p-doping of a halide perovskite surface using molecular dopants. Reproduced from Noel et al.^[47]. (D, E) UPS spectra of secondary electron cutoff region and valence band region of PTAA:F4TCNQ and perovskite films with and without 0.1 wt.% capsaicin grown on PTAA:F4TCNQ. (F) Cross-sectional atomic force microscopy topographies and corresponding KPFM images and potential profiles under zero-voltage bias of perovskite/PTAA:F4TCNQ/ITO without capsaicin. Reproduced from Xiong et al.^[48]. PSCs: Perovskite solar cells; KPFM: Kelvin probe force microscopy; UPS: ultraviolet photoelectron spectroscopy.