Efficient and Spectrally Stable Blue Light-Emitting Diodes Based on Diphenylguanidine Bromide Passivated Mixed-Halide Perovskites

An efficient and spectrally stable blue light-emitting diode is critical for realizing full-color emission and display of perovskite light-emitting diodes (PeLEDs). The band gap of mixed-halide perovskites can be easily tuned to emit pure and deep blue light; however, anion migration in perovskites under excitation and electronic fields results in poor stability of PeLEDs. Therefore, suppressing halide migration is crucial for the stability of mixed-halide blue PeLEDs. Herein, we introduce diphenylguanidine bromide (DPGABr) as a passivator to block the migration paths and immobilize halide anions through hydrogen bonding and electrostatic force between [PbX6]4– and DPGA+. The peak position and full width at half-maximum of the emitting spectrum of pure blue (474 nm) PeLEDs passivated by DPGABr remain constant at different voltages or upon 90 s constant bias of 4 V. A maximum external quantum efficiency of 3.07% is acquired in the sky blue (485 nm) mixed-halide PeLEDs.