Abstract: | A new transparent p‐type oxide semiconductor (POS) is reported, Cu2SnS3‐Ga2O3, having high Hall mobility of 36.22 cm2 V?1s?1, and high work function of 5.17 eV. The existence of Cu2SnS3 and Ga2O3 phases in the film is confirmed by X‐ray photoelectron spectroscopy results and the Cu2SnS3 shows polycrystalline structure according to Raman spectrum and X‐ray diffraction analysis. The transparent Cu2SnS3‐Ga2O3 exhibits the carrier concentration of 5.86 × 1016 cm?3, and electrical resistivity of 1.94 Ω·cm. The transparent POS is applied to green quantum light‐emitting diodes (QLEDs) as a hole injection layer (HIL) because of its high work function. The QLED exhibits the maximum current efficiency of 51.72 cd A?1, power efficiency of 31.97 lm W?1, and external quantum efficiency (EQE) of 14.93%, which are much higher than the QLED using polyethylene dioxythophene:poly(styrenesulfonate) HIL exhibiting current efficiency of 42.66 cd A?1, power efficiency of 20.33 lm W?1, and EQE of 12.36%. The Cu2SnS3‐Ga2O3 developed in this work can be widely used as a transparent and conductive p‐type oxide for thin‐film devices. |