Resurfacing halide perovskite nanocrystals

Metal halide perovskite semiconductors are ionic compounds with the formula AMX₃ (A and M are cations, and X can be Cl^-, Br^-, I^-, or binary mixtures of these anions). In the form of colloidal nanocrystals, these materials have extraordinary potential as light emitters. Not only do they exhibit high photoluminescence quantum yields (PLQYs), but the emission color can be finely tuned across the entire visible spectrum by changing the proportions of mixed halide anions (1). However, the surface chemistry of these nanocrystals makes them susceptible to degradation and long-term instability, and the surface can introduce surface centers (midgap states) that promote nonradiative recombination of charge carriers that lower PLQYs. Thus, the characterization of the interface between the perovskite nanocrystals and the organic ligands is fundamental to developing strategies to control surface defects, tuning the opto-electronic properties, and improving device performance and stability.