Metal halide perovskites for blue light emitting materials

Metal halide perovskites are considered excellent light emitting materials due to their high photoluminescence quantum yields, tunable spectral wavelength, and outstanding carrier transport properties. By taking advantage of these characteristics, perovskite light-emitting diodes (PeLEDs) can be fabricated via solution processing techniques. PeLEDs, thus, show great promise in display and lighting applications. Accordingly, external quantum efficiencies over 20% have been achieved in green- and red-PeLEDs. However, the performance of blue PeLEDs still lags far behind its red and green analogs. In this review, we summarize the recent progress of blue PeLEDs based on the halogen regulation strategy and the quantum confinement strategy. We discuss the challenges from aspects of poor charge injection, spectral instability, and high defect-states density encountered in blue PeLEDs. We make an outlook on feasible future research directions for highly efficient and stable blue PeLEDs.