Identifying and Reducing Interfacial Losses to Enhance Color-Pure Electroluminescence in Blue-Emitting Perovskite Nanoplatelet Light-Emitting Diodes.

Abstract

Perovskite nanoplatelets (NPls) hold promise for light-emitting applications, having achieved photoluminescence quantum efficiencies approaching unity in the blue wavelength range, where other metal-halide perovskites have typically been ineffective. However, the external quantum efficiencies (EQEs) of blue-emitting NPl light-emitting diodes (LEDs) have only reached 0.12%. In this work, we show that NPl LEDs are primarily limited by a poor electronic interface between the emitter and hole-injector. We show that the NPls have remarkably deep ionization potentials (≥6.5 eV), leading to large barriers for hole injection, as well as substantial non-radiative decay at the NPl/hole-injector interface. We find that an effective way to reduce these non-radiative losses is by using poly(triarylamine) interlayers. Using these, we increase the EQE of our blue LEDs emitting at 464 nm wavelength to 0.3%, as well as increase the EQE of our sky-blue-emitting LEDs to 0.55%. Our work also identifies the key challenges for further efficiency increases.