Overcoming the Charge Confinement-Transport Trade-Off in Perovskite Light-Emitting Diodes

Nanocrystalline metal halide perovskites are promising light emitters for light-emitting diodes (PeLEDs) because they suppress the intrinsic problem of exciton dissociation through charge confinement within nanocrystalline domains. Although these nanostructures have enabled high-emission efficiencies, such confinement strategies typically result in significantly reduced charge transport. This limitation is attributed to numerous grain boundaries, which induce severe charge carrier scattering and trapping, alongside insulating organic ligands typically introduced for defect passivation and size reduction. Poor charge transport increases the required operating voltage and accelerates device degradation pathways under an electrical bias, leading to limited operational lifetimes. This Review examines material design strategies intended to mitigate the competition between charge confinement and transport across various nanocrystalline perovskites. Specifically, we investigate fundamental crystal nucleation and growth mechanisms and evaluate methods to optimize grain size, aiming to minimize the grain boundary to increase charge transport while maintaining charge confinement. Passivation strategies for defect states are also evaluated, emphasizing the engineering of organic ligands to enhance their electrical conductivity while maximizing the passivation efficacy. In addition, the integration of core/shell architectures is discussed as a promising strategy. By controlling the shell composition, these structures promote efficient charge transport while maintaining high radiative recombination rates. Together, these material design strategies aim to overcome the confinement and transport trade-offs in PeLEDs.