Fig. 1
From: High efficiency perovskite quantum dot solar cells with charge separating heterostructure
Heterojunction structure of QD films. a Schematic overview of layer-by-layer assembly showing a perovskite QD film composed of different layers of QDs. MeOAc treatment is carried out between the deposition of different QD layers to remove the native oleate ligands and to render the deposited QDs insoluble in the solvent. b–d ToF-SIMS depth profile of samples with the structure and interface location indicated in the bar above the plots of CsPbI3/TiO2 (b), CsPbI3/Cs0.25FA0.75PbI3/TiO2 (c), and Cs0.25FA0.75PbI3/CsPbI3/TiO2 (d). All relevant elements from perovskite QD layer and TiO2 are shown. Compared to the structure without Cs0.25FA0.75PbI3, the FA signal shows a sharp and significant change and the Cs signal also shows a slight change at the boundary between the CsPbI3 and Cs0.25FA0.75PbI3 QD layers. The In signal is shown as a reference for when the ToF-SIMS profiling beam reaches the ITO on the substrate
