Suppressing interfacial nonradiative recombination by alkali hydroxides for efficient blue perovskite light-emitting diodes

Blue perovskite light-emitting diodes (PeLEDs) provide unlimited possibility in the field of optoelectronic devices due to their excellent characteristics. However, the widely used hole-transport material, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), has strong acidity and poor conductivity which deteriorate the efficiency and stability of perovskite devices. In this work, we modified PEDOT:PSS layer using alkalis, LiOH, NaOH, and KOH, to address these issues. Our findings indicated that the indium defect from indium tin oxide substrate was passivated after the introduction of LiOH, which resulted in the suppression of nonradiative recombination. In addition, the conductivity was improved owing to the increased phase separation of PEDOT:PSS. Taking advantage of optimized interface, the small-n phases of quasi-two-dimensional (quasi-2D) perovskite films were redistributed in quantities and dimensions. As results of these improvements, blue PeLEDs possessed the external quantum efficiencies of 5.95 % and an extended half-lifetime with emission-light wavelength of 473 nm. These findings offer an effective strategy to achieve highly efficient blue light-emitting diode.