Fig. 4: Photoluminescence quantum yield measurements (PLQY) and internal quasi-Fermi level splitting (QFLS) diagram.

a PLQY and QFLS diagram and VOC from JV results for perovskite film, perovskite/C60 half stack, and full cell with/without CB-NH2. The almost identical PLQY value between pero and pero/CB-NH2/C60 samples indicates the elimination of interfacial recombination. The bars represent the QFLS results from PLQY measurement and the stars the VOC from JV results, respectively. b Voltage loss mechanism for the control and CB-NH2-based samples. Source data are provided as a Source Data file.