Controllable Anion Exchange on Perovskite Nanocrystal Solid-State Thin Films

Colloidalmixed-halide perovskite nanocrystals (NCs) with a tunableemission color possess great potential for optoelectronic applications.However, their emission color and wavelength often change after purificationand thin film deposition steps. In this work, to circumvent the emissionshift issue, we report a novel method to directly tune the emissionwavelength through a controllable anion exchange process on perovskiteNC solid-state thin films. Specifically, it is realized by using hydrofluoroethersas the chemically benign reaction media with an organic halogen reagent.Our study also demonstrates that the phenylphosphonic halide reagent-relatedhydrolysis reaction is the dominant mechanism of anion exchange. Basedon the diversity of the halogen reagent, our anion-exchange approachshows good universality. Finally, as a proof of concept, colorfulRGB light-emitting diodes (LEDs) are fabricated, which shows the promisingpotential of our controllable anion-exchange strategy on perovskiteNC solid-state thin films and the compatibility with optoelectronicdevice applications.