In situ cadmium surface passivation of perovskite nanocrystals for blue LEDs

Abstract

Next-generation electroluminescent displays require efficient and stable red, green and blue light-emitting diodes (LEDs) with low cost, excellent color purity and flexibility, for which perovskite-based LEDs (PeLEDs) are a promising candidate. Among the three primary colors, the low efficiencies and poor stability of blue PeLEDs is the major hurdle to their commercialization. Here, we report an in situ surface engineering strategy incorporating a simple hot injection method with one pot synthesis for surface passivation of cadmium ions (Cd²⁺) into blue-emissive all-inorganic perovskite nanocrystals (PNCs). The optimized PNCs containing 0.2% Cd show improved photoluminescence quantum yield (PLQY; 66.8%) and ambient stability compared to the neat PNCs (25.5%) at an emission wavelength of 475 nm. PeLEDs with the PNCs show a luminance of 51 cd m⁻² and EQE of 3.71%. Through a series of ab initio calculations and comprehensive XPS analysis, we show that Cd incorporation into systems with reduced dimensionality such as PNCs likely takes place via surface inclusion in the perovskite B-site, which effectively suppresses the formation of halide defects and yields enhanced device efficiencies.