Tunable Angular Light Emission of Lead Halide Perovskite Nanocrystal Thin Films via Solution-Processed Substrate Treatment.

Lead halide perovskite (LHP) nanocrystals have demonstrated a significant electronic response to their local environment due to their ionic lattice nature. Here, we demonstrated their tunable dipole alignment via solution-processed methods. We synthesized LHP nanocubes and nanoplates in air and characterized them by UV-vis spectrophotometry and transmission electron microscopy. Using atomic force microscopy, UV-vis spectrophotometry, and back focal plane fluorescence microscopy, we characterized thin films of nanocubes on untreated glass, nanoroughened glass, and polymer film (poly-(methyl methacrylate), PMMA), as well as a perovskite nanocubes-nanoplate binary film on etched glass. Most notably, the dipole orientation factor can be modulated from 0.47 to 0.59 (effective transition dipole moment angle from 47° to 40°) by using glass or PMMA, respectively. Understanding the tunable anisotropic transitions in these materials at the nanoscale is required to control light emission into specific modes, which will maximize efficiency in devices such as light-emitting diodes, photovoltaics, and quantum information technology.