Bluish-white Light-emitting 2D Sheets of Lead-free Perovskite Cesium Titanium Bromide (CsTiBr) by a Two-stage Deposition Technique.

Bluish-white light-emitting materials are commonly used in LED lighting because they produce natural-looking light. Here we report the photoluminescent emission (PL) of novel, two-dimensional lead-free CsTiBr perovskite prepared via a two-stage deposition process. The formation of two-dimensional nanosheets of CsTiBr perovskite is confirmed by XRD, EDAX, and FESEM analysis. The height of the cesium bromide thin film substrate from the titanium bromide vapor source plays an important role in the formation of two-dimensional CsTiBr. The CsTiBr perovskite nanosheets exhibit unique exciton- luminescence at 440 nm and self-trapped exciton emission at 595 nm which are the characteristics of two-dimensional halide structure, along with the band-to-band emission at 400 nm at an excitation wavelength of 340 nm. The resulting bluish-white light PL emission makes two-dimensional CsTiBr perovskite an alternative material to the traditional lead-based perovskite in LEDs, display technology, solid-state lighting, and various optoelectronic devices, addressing environmental concerns.