Self-assembled methyl-ammonium lead bromide thin films with blue photoluminescence

Organic–inorganic metal halide perovskites (OIMHPs) are proving to be disruptive for the conventional silicon solar cell technology with conversion efficiencies breaching 29% using OIMHPs based hybrid structures. Synthesis of the colloidal Methyl-ammonium lead bromide (CH3NH3PbBr3) quantum dots was done using Ligand-Assisted re-precipitation strategy. Subsequently CH3NH3PbBr3 thin films were grown using these quantum-confined nano-particles by means of a simple solvent evaporation-induced self-assembly technique. Structural analyses of the colloidal nano-particles and thin films were done using High-Resolution Transmission Electron Microscopy (HR-TEM), X-ray diffraction and Raman spectroscopy. The crystal symmetry could be assigned to the Pnma space group with a = 7.94 A, b = 11.55 A and c = 8.15 A. Different to the green photoluminescence exhibited by bulk CH3NH3PbBr3, the thin films grown by us exhibit intense blue photoluminescence at a wavelength of ~ 488 nm with lower intensity emissions at ~ 463 nm and ~ 429 nm at room temperature. The uniqueness in blue emission from CH3NH3PbBr3 thin films grown by us is modeled based on the presence of excitons in this system.