Fused Carbazole-based Self-Assembled Monolayers Enable Efficient Perovskite Solar Cells and Perovskite Light-Emitting Diodes

Abstract

Carbazole-derived self-assembled monolayers (SAMs) with excellent hole-extraction and injection properties are promising hole-transporting materials for perovskite optoelectronic devices, including perovskite solar cells (PSCs) and perovskite light-emitting diodes (PeLEDs). The performance and thermal stability of these SAMs are heavily influenced by their chemical structure. Herein, the construction of fused carbazole-based SAMs is proposed by expanding the π-conjugation of the carbazole unit for application in PSCs and PeLEDs. Three proof-of-concept SAMs are designed and synthesized, termed XS8, XS9, and XS10, that feature highly rigid and planar fused carbazole as the donor and a conjugated alkene unit as the linker. This conjugated extension improves planarity, stability, and enhances the molecular dipole moment. Among these, XS10, with the highest degree of conjugation, demonstrated superior performance in perovskite-based devices. The PSC device utilizing XS10 achieves a maximum power conversion efficiency (PCE) of 20.28%, surpassing the 17.19% PCE of the classic 2PACz-based device. Similarly, the PeLED device with XS10 achieves a maximum external quantum efficiency (EQE) of 16.6%, compared to 14.5% for PEDOT-based devices. This work provides a novel molecular design strategy for creating efficient and stable SAMs for perovskite optoelectronics and other organic electronic devices.