Remote Tuning of Bandgap and Emission of Lead Perovskites by Spatially Controlled Halide Exchange Reactions

Local halide exchange reactions enable one to fabricate heterojunction perovskites; however, it is particularly challenging to deliver reactive halide precursors at the desired position. Here, we report an innovative approach for the fabrication of heterojunction perovskites by the localized halide exchange. We demonstrate the tuning of bandgap and the emission color of the desired domain in a lead halide perovskite microrod, which is realized by increasing the local concentration of the halide precursor under optical trapping using a nonresonant near-infrared laser beam. Similarly, the bandgap and the emission color of a crystal among several crystals are temporally tuned by a locally induced halide exchange reaction. Using this method, we overcome spontaneous halide exchange at undesired locations or crystals. We minimize photothermal and photochemical effects on halide exchange and photoinduced damage to the crystals by optical trapping using a 1064 nm continuous wave laser beam. The site-specific halide exchange offers flexible spatial control of bandgap and photoluminescence for designing perovskite-based heterojunction structures by laser scanning.