Multifunctional interfacial molecule for high-performance blue quantum dot light-emitting diodes

Abstract

Quantum dot light-emitting diodes (QLEDs) have emerged as promising candidates for next-generation displays. However, the realization of efficient blue devices remains challenging due to surface defects in quantum dots (QDs) and the intrinsically lower hole mobility compared to electron mobility. Here, we introduce an interface modifier, 4-bis 4-4-formylphenylphosphanylbenzaldehyde (FPPB), at the hole-transport layer (HTL)/emissive layer interface to address these challenges. The triple aldehyde electron (–CHO) withdrawing groups in FPPB effectively passivate surface defects in QDs, mitigating hydrolysis and oxidation of QDs. In addition, FPPB promotes a stepwise energy-level alignment at the HTL/QD interface, which facilitates hole injection and improves carrier balance in the devices. As a result, by optimizing FPPB concentration, the peak external quantum efficiency of QLEDs is significantly increased from 12.5% for the control device to 22.9% for 0.1 mg mL⁻¹ FPPB-incorporated device, with the maximum luminance increasing from 10 450 cd m⁻² to 23 370 cd m⁻², and lifetime (T₅₀ at 10 000 cd m⁻²) prolonged from 18.6 min to 55 min.