All-vacuum fabrication of yellow perovskite light-emitting diodes

Yellow light-emitting diodes (LEDs) are widely utilized in high-quality lighting, light communication, indicator lamps, etc. Owing to their outstanding material properties and device performance, the metal halide perovskites have demonstrated a significant potential for LED applications. However, the performance of the yellow perovskite LEDs (PeLEDs) is inferior to that of their green and red counterparts, with the maximum external quantum efficiency (EQE) limited to ∼3.1%. Further, a majority of the yellow PeLEDs are fabricated using the spin-coating methods. The current study reports the development of the yellow CsPbBr₂I PeLEDs based on an all-vacuum deposition approach, which has been widely employed in the commercial organic LEDs (OLEDs). By controlling the co-evaporation rate of CsI and PbBr₂, the growth kinetics of the perovskite layer are regulated to achieve a small grain size of ∼31.8 nm. Consequently, an improved radiative recombination rate (8.04 × 10^-9 cm³/s) is obtained owing to the spatial confinement effect. The PeLEDs based on the optimal perovskite film demonstrate the yellow electroluminescence (574 nm) with a maximum EQE of ∼3.7% and luminance of ∼16,200 cd/m², thus, representing one of the most efficient and bright yellow PeLEDs. Overall, this study provides a useful guideline for realizing the efficient PeLEDs based on the thermal evaporation strategy and highlights the potential of PeLED as an efficient and bright yellow light source.