High-Responsivity Gate-Tunable Ultraviolet-Visible Broadband Phototransistor Based on Graphene-WS 2 Mixed-Dimensional (2D-0D) Heterostructure

• Published in: ACS applied materials & interfaces Vol. 14; no. 4; pp. 5775 - 5784
• Main Authors: Mukherjee, Shubhrasish, Bhattacharya, Didhiti, Patra, Sumanti, Paul, Sanjukta, Mitra, Rajib Kumar, Mahadevan, Priya, Pal, Atindra Nath, Ray, Samit Kumar
• Format: Journal Article
• Language: English
• Published: United States 02.02.2022
• Subjects: mixed-dimensional heterostructure; phototransistor; broadband; WS2 quantum dots; graphene; stability
• DOI: 10.1021/acsami.1c18999
• ISSN: 1944-8244

Recent progress in the synthesis of highly stable, eco-friendly, cost-effective transition-metal dichalcogenide (TMDC) quantum dots (QDs) with their broadband absorption spectra and wavelength selectivity features have led to their increasing use in broadband photodetectors. With the solution-based processing, we demonstrate a superlarge (∼0.75 mm ), ultraviolet-visible (UV-vis) broadband (365-633 nm) phototransistor made of WS QDs-decorated chemical vapor deposited (CVD) graphene as the active channel with extraordinary stability and durability under ambient conditions (without any degradation of photocurrent until 4 months after fabrication). Here, colloidal zero-dimensional (0D) WS QDs are used as the photoabsorbing material, and graphene acts as the conducting channel. A high photoresponsivity (3.1 × 10 A/W), moderately high detectivity (∼8.9 × 10 Jones), and low noise equivalent power (∼9.7 × 10 W/Hz ) are obtained at a low bias voltage ( = 1 V) at an illumination of 365 nm with optical power as low as ∼0.8 μW/cm , which can be further tuned by modulating the gate bias. While comparing the photocurrent between two different morphologies of WS [QDs and two-dimensional (2D) nanosheets], a significant enhancement of photocurrent is observed in the case of QD-based devices. Ab initio density functional theory (DFT)-based calculations further support our observation, revealing the role of quantum confinement in enhanced photoresponse. Our work reveals a strategy toward developing a scalable, cost-effective, high-performance hybrid mixed-dimensional (2D-0D) photodetector with graphene-WS QDs for next-generation optoelectronic applications.