Enhanced Photoresponse of SnSe-Nanocrystals-Decorated WS₂ Monolayer Phototransistor

Abstract

Single-layer WS2 has shown excellent photoresponse properties, but its promising applications in high-sensitivity photodetection suffer from the atomic-thickness-limited adsorption and band-gap-limited spectral selectivity. Here we have carried out investigations on WS2 monolayer based phototransistors with and without decoration of SnSe nanocrystals (NCs) for comparison. Compared to the solely WS2 monolayer, SnSe NCs decoration leads to not only huge enhancement of photoresponse in visible spectrum but also extension to near-infrared. Under excitation of visible light in a vacuum, the responsivity at zero gate bias can be enhanced by more than 45 times to ∼99 mA/W, and the response time is retained in millisecond level. Particularly, with extension of photoresponse to near-infrared (1064 nm), a responsivity of 6.6 mA/W can be still achieved. The excellent photoresponse from visible to near-infrared is considered to benefit from synergism of p-type SnSe NCs and n-type WS2 monolayer, or in other words, the formed p-n heterojunctions between p-type SnSe NCs and n-type WS2 monolayer.

High-response hybrid quantum dots- 2D conductor phototransistors: recent progress and perspectives

“…Due to such high responsivities, the phototransistors do not require any amplifiers. Figure 5 shows that the responsivity is proportional to the drain-source voltage, V ds , in the wide range of V ds [10,17]. This dependence is highly expected because the transit time is inversely proportional to V ds , and therefore, the photoconductive gain is proportional to V ds , i.e.…”

“…SnSe nanocrystals were combined with WS 2 monolayer in Ref. [17]. Copper indium sulfide QDs deposited on SnS 2 were studied in Ref.…”

“…[10] (Figure 9B) and for phototransistors with WS 2 [17], SnS 2 [8], and MoS 2 [21] channels. The corresponding values of the exponent β in the dependence R ∝ P − 1 + β are summarized in Table 2.…”

Progress on Crystal Growth of Two-Dimensional Semiconductors for Optoelectronic Applications

“…A single channel photodetector whose channel is a metal diselenide compound possessed a balanced performance exhibiting faster optical response than disulfide (commonly~100 Hz), but lower responsivity in the visible wavelength. Other exfoliated 2D TMDCs such as WS 2 [121,122], GaSe [123], GaS [124], ReS 2 [115,125], In 2 Se 3 [98,126,127], MoSe 2 [128], GaTe [129] have also been reported in high gain n-channel photodetectors. Mobility of these synthetic materials and the quality of the semiconductor/oxide interface are very important for photodetectors based on the CVD method, while the device fabrication process is almost the same as that on exfoliated films.…”

“…For TMDCs, single channel photodetectors, CVD synthesis with solid-phase metal oxide and sulfur precursors are widely used because of the easy synthesis approach, large single crystal domain, and high mobility. Photodetectors based on CVD MoS 2 [113,131], MoSe 2 [132,133], ReS 2 [63,114], ReSe 2 [134], SnS 2 [135,136], SnSe 2 [137], and WS 2 [110,122] have been studied recently. Jing et al reported a MoS 2 phototransistor array that can detect room light illumination [138].…”