WO₃ nanobelt doped PEDOT:PSS layers for efficient hole-injection in quantum dot light-emitting diodes

Through a facile solid-state mechanochemical method, we have prepared WO₃ nanobelts with a length of ∼80 nm and a width of ∼10 nm, which were doped into PEDOT:PSS as a hybrid hole-injecting layer (HIL) for conventional red quantum dot light-emitting diodes (QLEDs). The work function (W_F) of the hybrid HIL was enhanced from 4.91 to 5.25 eV and the hole-injecting barrier was decreased from 0.89 to 0.55 eV. Notably, an optimal red QLED based on the hybrid HIL PEDOT:PSS:WO₃ (4.0 wt%) achieved a satisfactory reduction in the driving voltage at the luminance of 100 cd A^-1 from 5.18 V (pristine PEDOT:PSS) to 2.97 V. Moreover, the optimal device exhibits a maximal current efficiency of 15.5 cd A^-1 and a high external quantum efficiency (EQE) of 10.60%, which are nearly two-folds higher than those (8.0 cd A^-1 and 5.82%) of the reference device based on pristine PEDOT:PSS. It was demonstrated that doping these as-prepared WO₃ nanobelts into the PEDOT:PSS could be an effective route toward high-performance QLEDs.