Enhanced Conductivity and Tunable Work Function in VO_X Hole-Injection Layers via CsTFSI Doping for Efficient OLEDs

Balanced charge injection is critical for improving the performance of organic light-emitting diodes (OLEDs). However, hole-injection layer (HIL) materials often suffer from low conductivity and mismatched energy levels, both of which limit hole injection. Herein, we develop an effective strategy using Cesium(I) Bis(trifluoromethanesulfonyl)imide (CsTFSI) to regulate the characteristics of VO_X HIL. The energy level alignment and electrical conductivity can be readily tuned by adjusting the doping concentrations of CsTFSI. The optimized device performance is attributed to the synergistic effects of enhanced HIL conductivity and favorable energy level alignment. With fine-tuned HIL, the OLEDs achieved the maximum current efficiency of 67.68 cd A⁻¹ and maximum external quantum efficiency of 19.67%, which represent improvements of 23.4% and 26.3% respectively compared to devices with undoped VO_X HIL. This work highlights CsTFSI doping as a promising approach for developing high-performance VO_X HILs.