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.