Dimensionality Controls Anion Intermixing in Electroluminescent Perovskite Heterojunctions

Metal halide perovskites have emerged as a promising group of materials for optoelectronic applications such as photovoltaics, light emission, and photodetectors. So-far, in particular, the stability of light-emitting devices is limited, which is in part attributed to the intrinsic ionic conductivity of these materials. High-performance devices inevitably contain heterojunctions similar to other optoelectronic devices based on oxide perovskites, II–VI, or III–V group semiconductors. To enable efficient heterojunctions, ion exchange at the interface between different layers should be controlled. Herein, we report a method that enables to control and monitor the extent of anion intermixing between solution-processed lead bromide and vacuum-deposited lead chloride perovskite films. Taking advantage of the ability to fine tune the layer thicknesses of the vacuum-deposited films, we systematically study the effect of film thickness on anionic intermixing. Using these multiple layers, we prepare proof of principle light-emitting devices exhibiting green and blue electroluminescence.