Proceedings of International Conference on Perovskite Thin Film Photovoltaics, Photonics and Optoelectronics (ABXPV18PEROPTO)
DOI: https://doi.org/10.29363/nanoge.abxpvperopto.2018.075
Publication date: 11th December 2017
This work showcases our research on modification of compact TiO2 electron transport layers (ETLs) at the TiO2/CH3NH3PbI3 interface for application in planar lead halide perovskite solar cells. Compact TiO2 ETLs were formed via spraying of a commercially available titanium diisopropoxide bis(acetylacetonate) precursor on fluorine-doped tin oxide (FTO) glass followed by annealing at 550 C. These layers were subsequently spin coated with aqueous solutions of 10mM and 40mM of KX (X = Cl-, I-, Br-, prior to CH3NH3PbI3 deposition. Presence of potassium and X- ions on the TiO2 surface is evident via X-ray photoelectron spectroscopy (XPS) analysis, and individual crystals can be seen on the modified TiO2 films via scanning electron microsope (SEM) images. Furthermore, the KX crystals provide a template for denser crystallization of the overlying CH3NH3PbI3 layers resulting in higher perovskite coverage and reduction in pinhole density, as compared to untreated TiO2/CH3NH3PbI3 films. For KCl and KI treated layers the CH3NH3PbI3 grain size is higher for 40 mM compared to 10 mM treatment; however for KBr treated layers, the grain size does not change significantly between the two treatments. The absorbance of TiO2/KX/ CH3NH3PbI3 films does not show much difference, however photoluminescence spectra show improved photoluminescence quenching for the all modified TiO2/KX/ CH3NH3PbI3 films compared to the TiO2/CH3NH3PbI3. Preliminary results show that against a stabilized power conversion efficiency of 8.25% in the reverse direction for unmodified planar devices, KI modified devices reach up to 11.57%, followed by KBr at 10.22%. and finally KCl at 8.09% .