Ultrasensitive photodetector based on 2D WS₂/AgInGaS quantum dots heterojunction with interfacial charge transfer

Abstract Tungsten disulfide (WS₂), as a typical member of transition metal chalcogenides (TMDs), has attracted extensive research interest in optoelectronics, especially photodetectors. However, the performance of photodetectors based on monolayer WS₂ is restricted to weak light absorption. Here, AgInGaS quantum dots (AIGS-QDs) with a large absorption coefficient and high quantum efficiency are integrated onto WS₂ atomic layers to achieve excellent photoelectric performance. Notably, the observed photoluminescence (PL) quenching and the reduction of the decay time of PL in the WS₂/AIGS-QDs heterojunction confirm the interfacial charge transfer from AIGS-QDs to WS₂ layer. The results show that type II energy band arrangement leads to the efficient separation of photoexcited carriers at the interface between WS₂ and AIGS-QDs. This WS₂/AIGS-QDs photodetector achieves an ultrahigh responsivity (R) of 3.3 × 10³ A W⁻¹, an external quantum efficiency (EQE) of 7.8 × 10⁶% and a detectivity (D*) of 1.3 × 10¹³ Jones. Our work provides promising potential for future high-performance monolayer TMD-based photodetectors.