This paper presents the fabrication and characterization of a single-layer MoS₂ phototransistor. The device is fabricated using mechanically exfoliated single-layer MoS₂ nanosheets and exhibits excellent light-induced electric properties. The photocurrent generated by the phototransistor is solely dependent on the illuminated optical power at a constant drain or gate voltage. The switching behavior of photocurrent generation and annihilation occurs within approximately 50 ms, demonstrating good stability. The single-layer MoS₂ phototransistor shows superior photoresponsivity compared to graphene-based devices, reaching up to 7.5 mA/W under low optical power and medium gate voltage. The unique characteristics of the device, including incident-light control, prompt photoswitching, and good photoresponsivity, make it a promising candidate for developing multi-functional optoelectronic devices. The study highlights the potential of single-layer semiconducting materials in advanced optoelectronic applications.This paper presents the fabrication and characterization of a single-layer MoS₂ phototransistor. The device is fabricated using mechanically exfoliated single-layer MoS₂ nanosheets and exhibits excellent light-induced electric properties. The photocurrent generated by the phototransistor is solely dependent on the illuminated optical power at a constant drain or gate voltage. The switching behavior of photocurrent generation and annihilation occurs within approximately 50 ms, demonstrating good stability. The single-layer MoS₂ phototransistor shows superior photoresponsivity compared to graphene-based devices, reaching up to 7.5 mA/W under low optical power and medium gate voltage. The unique characteristics of the device, including incident-light control, prompt photoswitching, and good photoresponsivity, make it a promising candidate for developing multi-functional optoelectronic devices. The study highlights the potential of single-layer semiconducting materials in advanced optoelectronic applications.