P-type doping strategy for hole-transport polymer in blue perovskite light-emitting diodes

The inferior hole injection efficiency in blue perovskite light-emitting diodes (PeLEDs), caused by the large hole injection barrier and low hole mobility of conventional hole transport layers (HTLs), remains a critical limitation to achieving higher external quantum efficiency (EQE) and device stability. To address this challenge, we propose a rational interfacial engineering strategy employing p-type molecular doping to optimize device performance. By incorporating 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone (F4TCNQ) as a dopant in the poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) HTL, we significantly enhance hole mobility from 3.96×10⁻⁶ to 1.13×10⁻⁴ cm²/(V·s) and adjust the highest occupied molecular orbital energy level from -5.40 to -5.56 eV, facilitating efficient hole carrier injection and transport. Additionally, perovskite films deposited on the doped HTL exhibit improved crystallinity and a reduced defect density from 3.47×10¹⁸ to 3.18×10¹⁷ cm⁻³. Owing to these synergistic improvements, the optimized blue PeLEDs achieve a maximum EQE of 4.57% with an emission peak at 484 nm, representing a 4.02-fold enhancement over the pristine device. This work highlights the effectiveness of molecular doping in tailoring interfacial properties and balancing charge transport for high-performance blue PeLEDs.