Controllable Anion Exchange on Perovskite Nanocrystal Solid-State Thin Films

Colloidal mixed-halide perovskite nanocrystals (NCs) with a tunable emission color possess great potential for optoelectronic applications. However, their emission color and wavelength often change after purification and thin film deposition steps. In this work, to circumvent the emission shift issue, we report a novel method to directly tune the emission wavelength through a controllable anion exchange process on perovskite NC solid-state thin films. Specifically, it is realized by using hydrofluoroethers as the chemically benign reaction media with an organic halogen reagent. Our study also demonstrates that the phenylphosphonic halide reagent-related hydrolysis reaction is the dominant mechanism of anion exchange. Based on the diversity of the halogen reagent, our anion-exchange approach shows good universality. Finally, as a proof of concept, colorful RGB light-emitting diodes (LEDs) are fabricated, which shows the promising potential of our controllable anion-exchange strategy on perovskite NC solid-state thin films and the compatibility with optoelectronic device applications.