Enhancing the properties of perovskite quantum dot light emitting devices through grid structures formed by trioctylphosphine oxide

Abstract

Surface engineering and doping are common methods used to enhance the emission properties of perovskite quantum dot light-emitting diodes (PeQLEDs), and more effective methods need to be developed. Here, we introduce a spin-coated trioctylphosphine oxide (TOPO) layer that spontaneously forms concave–convex micro grid structures between the hole-transport layer (TFB) and the CsPbBr₃ quantum dot (QD) layer. The unique concave–convex micro grid structures change with the concentration of TOPO solution and the type of solvent, which may be caused by the surface tension. Spectral measurements reveal that the TOPO layer passivates the surface defects between the perovskite QDs. The finite-difference-time-domain (FDTD) method proves that these concave–convex micro grid structures also increase light output from the quantum dot light-emitting diodes (QLEDs). As a result, green perovskite QD light emitting diodes (LEDs) of 514 nm with a Luminous Efficiency (LE) of 3975 cd m⁻², Current Efficiency (CE) of 18.8 cd A⁻¹ and External Quantum Efficiency (EQE) of 6.7% can be achieved, which are improved three-fold compared to the CsPbBr₃ QLEDs without the TOPO layer. Our work suggests that the micro grid structures of the TOPO layer provide a novel and facile way to enhance the performance of the perovskite QLEDs.