Morphology and optical studies of Cr doped TiO2 and Mixed-Halide Perovskite coated rutile TiO2 nanorods

Abstract Present study deals with synthesis and characterization of Cr doped TiO 2 layer in multilayer structure including nanorods and light harvesting active layer. Effect of Cr on crystallinity, Raman shift and optical absorbance is presented. Surface morphology of the coating of pure and Cr doped TiO 2 layers were strongly affected by the morphology of the underneath nanorods. Role of the dandelion structures formed on the surface of the vertically aligned nanorods, have been investigated in terms of morphology of multiple layer coatings. In the vicinity of the dandelion structures, coating of the layer was thick while regions away from dandelion structures had thinner coating. Overall results show that pure and Cr doped TiO 2 layers exhibit inhomogeneities whose features are very much universal, for the given dilution of the spin coated solution. In the cases of thicker coating, cracks were obvious which was true for all concentrations of Cr. Similar trend was exhibited by methyl ammonium lead mixed halide (CH 3 NH 3 PbI 3-x Cl x ) coated on TiO 2 , however effects were magnified in comparison with Cr doped TiO 2 coating. Locally thickness of the coated layer depends on size and density of the dandelion regions. Consistent increase in absorbance in the visible region have been observed with Perovskite addition which further varies with the addition of Cr doped layer in trilayer structure being a signature of band alignment modification. Morphological issues have been identified and possible solutions are suggested.