Inorganic hole transport layers for perovskite light-emitting diodes: from material design to interfacial kinetics regulation

Abstract

Perovskite light-emitting diodes (PeLEDs) have emerged as a promising technology for next-generation displays. However, the widely employed organic hole transport layers (HTLs) in PeLEDs suffer from inherent drawbacks, such as thermal instability and low carrier mobility, which severely constrain their commercial viability. Although inorganic HTLs offer a robust solution, a systematic framework linking their physicochemical properties to interfacial dynamics is lacking. This review critically assesses the state-of-the-art inorganic HTLs, comprehensively categorizing them into copper-based compounds, nickel oxides, transition metal oxides, and emerging candidates. Beyond material categorization, we dissect the critical interface regulation mechanisms essential for high-performance devices. These specifically involve mitigating interfacial carrier accumulation to suppress non-radiative recombination, leveraging HTLs as growth templates to modulate perovskite crystallization kinetics, and immobilizing metal ions to inhibit detrimental migration. By elucidating these physicochemical interactions, we provide theoretical insights and design guidelines for engineering stable, high-efficiency inorganic HTLs for PeLEDs.