Blue-Green Color Tunable Solution Processable Organolead Chloride–Bromide Mixed Halide Perovskites for Optoelectronic Applications

Solution-processed organo-lead halide perovskites are produced with sharp, color-pure electroluminescence that can be tuned from blue to green region of visible spectrum (425–570 nm). This was accomplished by controlling the halide composition of CH₃NH₃Pb­(Br_<i>x</i>Cl_1–<i>x</i>)₃ [0 ≤ <i>x</i> ≤ 1] perovskites. The bandgap and lattice parameters change monotonically with composition. The films possess remarkably sharp band edges and a clean bandgap, with a single optically active phase. These chloride–bromide perovskites can potentially be used in optoelectronic devices like solar cells and light emitting diodes (LEDs). Here we demonstrate high color-purity, tunable LEDs with narrow emission full width at half maxima (FWHM) and low turn on voltages using thin-films of these perovskite materials, including a blue CH₃NH₃PbCl₃ perovskite LED with a narrow emission FWHM of 5 nm