Gold Nanoparticles Embedded in PEDOT:PSS for Enhanced Hole Injection and Negligible Exciton Quenching in OLEDs

Gold nanoparticles (AuNPs) can improve hole injection in OLEDs but may also induce LSPR-related optical perturbation and exciton quenching. To exploit their hole-injection-promoting effect while suppressing possible exciton quenching, AuNPs with diameters of 3.5–4.0 nm were synthesized by citrate reduction and doped into PEDOT:PSS as a hole injection layer modifier. Photoluminescence measurements revealed absorption-related wavelength-dependent optical perturbation from exposed AuNPs, with the strongest effect on red emission and only a minor effect on blue emission. AuNPs embedded in PEDOT:PSS caused only slight changes in PL spectra and PL decay behavior, indicating that obvious exciton quenching was avoided. OLEDs with AuNP-doped PEDOT:PSS exhibited reduced turn-on voltages and increased maximum current efficiencies from 22.4 to 27.0 cd/A, 7.64 to 15.6 cd/A, and 16.8 to 29.0 cd/A for blue, red, and green devices, respectively. These results indicate that sub-5 nm AuNPs embedded in PEDOT:PSS can improve device performance by enhancing hole-injection capability, while their wavelength-dependent exciton-quenching effect is negligible.