Spin coating epitaxial heterodimensional tin perovskites for light-emitting diodes

Environmentally friendly tin (Sn) perovskites have received considerable attention due to their great potential for replacing their toxic lead counterparts in applications of photovoltaics and light-emitting diodes (LEDs). However, the device performance of Sn perovskites lags far behind that of lead perovskites, and the highest reported external quantum efficiencies of near-infrared Sn perovskite LEDs are below 10%. The poor performance stems mainly from the numerous defects within Sn perovskite crystallites and grain boundaries, leading to serious non-radiative recombination. Various epitaxy methods have been introduced to obtain high-quality perovskites, although their sophisticated processes limit the scalable fabrication of functional devices. Here we demonstrate that epitaxial heterodimensional Sn perovskite films can be fabricated using a spin-coating process, and efficient LEDs with an external quantum efficiency of 11.6% can be achieved based on these films. The film is composed of a two-dimensional perovskite layer and a three-dimensional perovskite layer, which is highly ordered and has a well-defined interface with minimal interfacial areas between the different dimensional perovskites. This unique nanostructure is formed through direct spin coating of the perovskite precursor solution with tryptophan and SnF₂ additives onto indium tin oxide glass. We believe that our approach will provide new opportunities for further developing high-performance optoelectronic devices based on heterodimensional perovskites.