Fig. 4From: In Situ-Formed and Low-Temperature-Deposited Nb:TiO2 Compact-Mesoporous Layer for Hysteresis-Less Perovskite Solar Cells with High Performancea The absorption spectra of the FTO substrate, TiO2/FTO, and 2% Nb:TiO2/FTO. b Tauc-plots of the FTO substrate, TiO2/FTO, and 2% Nb:TiO2/FTOBack to article page