Palladium diselenide (PdSe 2 ), a thus far scarcely studied group-10 transition metal dichalcogenide has exhibited promising potential in future optoelectronic and electronic devices due to unique structures and electrical properties. Here, the controllable synthesis of wafer-scale and homogeneous 2D PdSe 2 film is reported by a simple selenization approach. By choosing different thickness of precursor Pd layer, 2D PdSe 2 with thickness of 1.2-20 nm can be readily synthesized. Interestingly, with the increase in thickness, obvious redshift in wavenumber is revealed by Raman spectroscopy. Moreover, in accordance with density functional theory (DFT) calculation, optical absorption and ultraviolet photoemission spectroscopy (UPS) analyses confirm that the PdSe 2 exhibits an evolution from a semiconductor (monolayer) to semimetal (bulk). Further combination of the PdSe 2 layer with Si leads to a highly sensitive, fast, and broadband photodetector with a high responsivity (300.2 mA W −1 ) and specific detectivity (≈10 13 Jones). By decorating the device with black phosphorus quantum dots, the device performance can be further optimized. These results suggest the asselenized PdSe 2 is a promising material for optoelectronic application.

Group-10 layered transitional metal dichalcogenides including PtS2, PtSe2 and PtTe2 are excellent potential candidates for optoelectronic devices due to their unique properties such as high carrier mobility, tunable bandgap, stability and flexibility. Large-area platinum diselenide (PtSe2) with semiconducting characteristics is far scarcely investigated. Here, we report on the development of a high performance photodetector based on vertically aligned PtSe2-GaAs heterojunction which exhibited a broadband sensitivity from deep ultraviolet (DUV) to near infrared (NIR) light, with peak sensitivity from 650 to 810 nm. The Ilight/Idark ratio and responsivity of photodetector were 3×10 4 and 262 mA W −1 measured at 808 nm under zero bias voltage. The response speed of τr/τf were 5.5/6.5 μs, which represented the best result achieved for Group-10 TMDs based optoelectronic device thus far. According to first-principle density functional theory, the broad photoresponse ranging from visible to near infrared region is associated with the semiconducting characteristics of PtSe2 which has interstitial Se atoms within the PtSe2 layers. It was also revealed that the PtSe2/GaAs photodetector did not exhibit performance degradation after 6 weeks in air. The generality of the above good results suggests that the vertically aligned PtSe2 is an ideal material for high-performance optoelectronic systems in the future.

In this study, we present a photodetector based on a topological insulator Sb2Te3 thin film, which shows an obvious photoresponse to near infrared light with good responsivity, photoconductive gain and detectivity.

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