All-Perovskite Emission Architecture for White Light-Emitting Diodes.

We demonstrate all-perovskite light-emitting diodes (PeLEDs) with white emission on the basis of simultaneously solving a couple of issues including the ion exchanges between different perovskites, solvent incompatibility in the solution process of stacking different perovskites and carrier transport layers, as well as the energy level matching between each layer in the whole device. The PeLEDs are built with a two-dimensional (CH3CH2CH2NH3)2CsPb2I7 perovskite that emits red light, CsPb(Br,Cl)3 quantum dots that emit a cyan color, and an interlayer composed of bis(1-phenyl-1H-benzo[ d]imidazole)phenylphosphine oxide (BIPO) and poly(4-butylphenyl-diphenyl-amine) (Poly-TPD). The interlayer is designed to realize desirable white electroluminescence by tuning the electron and hole transportation and distribution in-between multilayers. With this PeLED configuration, we achieve the typical white light with chromaticity coordinates of (0.32, 0.32) in Commission Internationale de L'Eclairage (CIE) 1931 color space diagram and steady CIE coordinates in a wide range of driving current densities (from 2.94 to 59.29 mA/cm2). Consequently, our work, as the starting point for future research of all-perovskite white PeLEDs, will contribute to the future applications of PeLEDs in lighting and display. In addition, we believe that the proposed material and all-perovskite concept will leverage the design and development of more perovskite-based devices.