Colloidal Halide Perovskite Nanoplatelets: An Exciting New Class of Semiconductor Nanomaterials

Abstract

Metal halide perovskites are a family of semiconductor materials with exciting properties such as long charge carrier diffusion lengths, ease of synthesis and composition tunability, and remarkable defect tolerance. Recently, methods have been developed to synthesize metal halide perovskites in the form of colloidal nanosheets—or nanoplatelets—which are only a few unit cells in thickness and, as a result, experience the effects of strong dielectric and quantum confinement. This leads to narrow and blue-shifted absorption/emission as compared to the bulk state—allowing lead bromide and lead iodide nanoplatelets to cover the entire visible range. In contrast to bulk crystals, nanoplatelets exhibit strongly excitonic properties and enhanced radiative recombination. In this article we present an overview of colloidal perovskite nanoplatelets: how they are made, what their capabilities are, why 2D is beneficial, and where these materials are headed. We draw analogues to solid phase layered perovskites, cadmium selenide nanoplatelets, and 2D transition metal dichalcogenides to emphasize some of the most promising attributes of 2D materials such as their penchant for directional emission, fast/directional energy transfer, strong exciton binding energy, and reduced dielectric screening effects. We discuss the interesting physics present in these materials, remaining stability issues, and the future applications for nanoplatelets in LEDs, photovoltaics, photodetectors, and lasers.