A crystallographic model for the CH3NH3Pb(I,Clx)3-x/TiO2 interface and the effect of chlorine on the electron density distribution in perovskite solar cells

• Crystallographic characteristics of the CH3NH3PbI3/ TiO2 interface. • Determined a minimum energy distance of 2.871 Å between the perovskite and TiO2. • lattice mismatch between CH3NH3PbI3 and TiO2 was calculated to be 4.46%. • interactions at the interface occur between oxygen and either iodine or chlorine • TiO2 exhibits charge depletion behavior, while the perovskite demonstrates charge accumulation An atomic model of the CH 3 NH 3 Pb(I,Cl x ) 3-x /TiO 2 interface, which constitutes the n-i junction in hybrid perovskite solar cells, was developed based on the high-resolution transmission microscopy (HRTEM) images and X-ray diffraction (XRD) data. This model enables a crystallographic interpretation of these materials. Although they are susceptible to degradation under the electron beam during transmission electron microscope (TEM) analysis, HRTEM images still permit the observation and structural study of moiré patterns, double diffraction, and dislocations along the [1 1 ¯ 2 ¯ ] zone axis. Based on the proposed model, computer simulations of the interface reveal moiré patterns caused by a 7.6° rotation between the two materials, as well as dislocations resulting from lattice mismatch. Theoretical calculations, including Morse potential, projected density of states (PDOS), and electron density difference isosurfaces (Δρ diff ), were carried out for both the CH 3 NH 3 PbI 3 /TiO 2 and CH 3 NH 3 Pb(I,Cl x ) 3-x /TiO 2 interfaces. The results indicate that the presence of chlorine enhances the electron density distribution.