Fig. 1. Schematic diagram of the process for the preparation of LiCl-PEDOT∶PSS film

Fig. 2. SEM images of the PEDOT∶PSS films with various LiCl doping content（mass fraction）.（a）0%；（b）1%；（c）2%；（d）3%.

Fig. 3. 2D（top）and 3D（bottom）AFM images of the PEDOT∶PSS films with various LiCl doping content（mass fraction）.（a，e）0%；（b，f）1%；（c，g）2%；（d，h）3%.

Fig. 4. （a）Current-voltage（I-V）curves of the ITO/LiCl-PEDOT∶PSS/Al device with various LiCl doping content（mass fraction）；（b）Transmittance spectra of the PEDOT∶PSS films with various LiCl doping content（mass fraction）.

Fig. 5. Schematic diagram of the binding for anion and cation to PEDOT∶PSS after LiCl doping

Fig. 6. Schematic diagrams of the structure（a）and energy level（b）of the QLED device based on LiCl-PEDOT∶PSS HIL

Fig. 7. Electroluminescence characteristics of the blue QLEDs with different LiCl content（mass fraction）.（a）J-V curves；（b）L-V curves；（c）CE-J curves；（d）PE-J curves；（e）EQE-J curves；（f）EQE-L curves.

Fig. 8. （a）Statistical plots of peak EQE from 8 identical devices for QLEDs with different LiCl contents（mass fraction）.（b）Schematic diagram of the structure and（c）the J-V curves of the single-hole devices（ITO/PEDOT∶PSS（without or with LiCl doping）/TFB/PVK/QDs/MoO₃/Al）.

Fig. 9. Normalized EL spectra of the QLED devices under various driving voltages without（a）and with（b）LiCl doping

Fig. 10. CIE color coordinates corresponding to the EL spectra of QLED with 2%（mass fraction）LiCl under a driving voltage of 7 V（Inset：the photograph of a working QLED device）