Dual functionality of carbazole-based phosphonic acid molecular additives realizes efficient hole transport layer-free perovskite light-emitting diodes

Abstract

Traditionally, perovskite light-emitting diodes (PeLEDs) have used complex and costly hole transport layers (HTLs), but these materials pose a significant challenge to commercialization due to their synthetic complexity and energy-intensive deposition processes. Eliminating the use of HTLs can effectively reduce manufacturing costs and simplify device production. Here, we present a simple method to achieve efficient HTL-free devices by exploiting the self-assembly property of carbazole-based phosphonic acid (PACz) molecules to address the issues of poor hole injection and charge imbalance in HTL-free PeLEDs. The results show that the self-assembly property and defect passivation effect of PACz molecules significantly improve the device performance. The self-assembly of some molecules on the ITO substrate creates hole-selective contacts and lowers the hole injection barrier. This facilitates hole injection and radiative recombination. Meanwhile, due to the interaction between P=O (and/or halide headgroup) and perovskite, some molecules incorporated in perovskite effectively passivate the uncoordinated Pb2+ and halide vacancies. As a result, efficient HTL-free PeLEDs were realized by incorporating PACz molecules into perovskites. © 2024 Elsevier B.V.