Dipole-molecular buffer interface engineering for mitigating hole injection barrier and interface defect in high-efficiency quasi-2D blue perovskite light-emitting diodes

The quasi-two-dimensional (quasi-2D) perovskites, characterized by strong quantum confinement and high exciton binding energy, hold significant promise for blue perovskite light-emitting diodes (PeLEDs). However, challenges including imbalanced charge injection and defect-related nonradiative recombination at the interface, particularly at the hole transport layer (HTL)/perovskite interface, hinder the development of efficient PeLEDs. This investigation systematically evaluates the effect of various dipolar molecules on the HTL/perovskite interface, aiming to enhance the efficiency of blue PeLEDs. The results indicate that the hole injection barrier of devices modified with diethyl difluoromethanephosphonate (DFMP) was significantly reduced due to the high polarity of DFMP, which maintains a balanced hole–electron mobility. Furthermore, the electron-rich P=O bond in DFMP effectively coordinates with the unsaturated Pb2+ at the buried interface to passivate defects that contribute to radiative recombination. As a result, the DFMP-modified PeLEDs achieve a peak external quantum efficiency of 9.8% at 480 nm and a prolonged operational lifetime. The study paves the way for interfacial molecular buffer layers to interface modulation in quasi-2D PeLEDs.