Lateral 2D WSe₂ p–n Homojunction Formed by Efficient Charge‐Carrier‐Type Modulation for High‐Performance Optoelectronics

Abstract As unique building blocks for next‐generation optoelectronics, high‐quality 2D p–n junctions based on semiconducting transition metal dichalcogenides (TMDs) have attracted wide interest, which are urgent to be exploited. Herein, a novel and facile electron doping of WSe₂ by cetyltrimethyl ammonium bromide (CTAB) is achieved for the first time to form a high‐quality intramolecular p–n junction with superior optoelectronic properties. Efficient manipulation of charge carrier type and density in TMDs via electron transfer between Br⁻ in CTAB and TMDs is proposed theoretically by density functional theory (DFT) calculations. Compared with the intrinsic WSe₂ photodetector, the switching light ratio (I_light/I_dark) of the p–n junction device can be enhanced by 10³, and the temporal response is also dramatically improved. The device possesses a responsivity of 30 A W⁻¹, with a specific detectivity of over 10¹¹ Jones. In addition, the mechanism of charge transfer in CTAB‐doped 2D WSe₂ and WS₂ are investigated by designing high‐performance field effect transistors. Besides the scientific insight into the effective manipulation of 2D materials by chemical doping, this work presents a promising applicable approach toward next‐generation photoelectronic devices with high efficiency.