Molecularly Engineered Self-Assembled Monolayer Interfaces for Efficient and Stable Green Perovskite LEDs

Perovskite light-emitting diodes (PeLEDs) are promising candidates for next-generation displays owing to their narrow emission linewidth, wide color gamut, and low-temperature solution processing. Efficient, stable green PeLEDs require a bottom hole-transport interface with favorable energy level alignment and uniform hole injection that suppresses interfacial recombination. Self-assembled monolayers (SAMs) are attractive hole-transport layers owing to their ultrathin, conformal nature and tunable interfacial dipoles, but conventional SAM molecules tend to aggregate in solution, causing incomplete and non-uniform adsorption on transparent conducting oxides. The resulting energetic disorder creates hole-injection barriers and trap states at the buried interface, leading to charge imbalance, trap-assisted recombination, efficiency roll-off, and limited stability.

Here, we develop a molecularly engineered SAM-based HTL for green PeLEDs. Dynamic light scattering and molecular simulations reveal improved solution-state dispersion of the SAM molecules, while surface and photoelectron analyses show enhanced coverage, stronger interfacial binding, a favorable work function shift, and a uniform contact-potential distribution. Photoluminescence, electrical, and transient electroluminescence analyses consistently indicate suppressed trap-assisted recombination and balanced hole injection. The engineered SAM enables green PeLEDs with a maximum EQE of 25.7% and a T₅₀ of 4.5 h at 100 cd m⁻², a significant improvement over control devices, demonstrating molecular-level SAM engineering as an effective route toward efficient, stable PeLEDs.