Effect of substrate inclination angle on the evaporation-induced self-assembly of CsPbBr3 thin films

Inorganic metal halide perovskites have significant interest due to their wide applications in optoelectronics. The effect of substrate immersion angle on the evaporation-induced self-assembly of Cesium lead bromide (CsPbBr3) thin films on a glass substrate is reported in this work. Colloidal CsPbBr3 nano-crystals synthesized through the Ligand Assisted Re-precipitation (LARP) method under ambient conditions are used for self-assembly. Structural, morphological, and optical properties of the self-assembled thin films are investigated using TEM, XRD, FE-SEM, AFM, Raman, UV-visible absorption, and Photoluminescence techniques. Thin films self-assembled on a substrate inclined at 90° show the best crystallinity, larger optical band gap, and minimum grain size relative to films grown with an inclination of 0° and 45°. Self-assembled thin films exhibit preferential growth along the (004) and (220) planes for a substrate inclination angle of 90°. C-axis growth was favored when the substrate was inclined at 450. The optical band gap of the self-assembled 2D material was found to increase as the substrate angle was increased from 0° to 90°. The recombination lifetime in these self-assembled CsPbBr3 thin films was found to be ∼14 ns, exhibiting a 68% reduction relative to that measured for the colloidal nanocrystals. A shelf life of over 6 months for the self-assembled thin films with no significant degradation in their structural and optical properties has been reckoned by us presently.