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

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.