Fig. 2: SnO2 buffer layer.

a Cutoff (left) and valance (right) spectra of ITO/PEDOT:PSS/TFB/QD, ITO/PEDOT:PSS/TFB/QD/SnO2, ITO/PEDOT:PSS/TFB/QD/SnO2/s-ZnO. b The optical bandgap of the QD, SnO2, and s-ZnO films. c The energy-level alignment of a QD/SnO2/s-ZnO stack which is deposited on an ITO/PEDOT:PSS/TFB substrate. d TRPL of QDs on quartz, QDs on s-ZnO/quartz at Day 0 and Day 7. e TRPL of QD on quartz, QD on s-ZnO/SnO2/quartz at Day 0 and Day 7.