Fig. 1. (a) Schematic diagram of plasmonic CuInSe2 QD FEpT architecture. (b) Cross-sectional SEM image of composite film between CuInSe2 and Au NPs (inset: TEM image of pristine CuInSe2 QDs). (c) AFM image of Au NPs on silicon substrate. (d) Optical absorption spectra of CuInSe2 QDs with (red line) and without (black line) deposited Au NPs on glass substrate.

Fig. 2. Photoelectronic properties of the device. (a) Output characteristics (IDS−VDS curves) under different VGS (1 V increment) of plasmonic FEpT (dashed lines, in darkness; solid lines, under illumination of 700  mW·cm−2 of a 405 nm laser). (b) Transfer characteristics of typical CuInSe2 FEpTs, after Au NP deposition (black line, in darkness; red line, under illumination of an 845  mW·cm−2 of 808 nm laser) and before Au NPs deposition (blue line, in darkness; green line, under illumination of 845  mW·cm−2 of an 808 nm laser) with applied bias voltage VDS=1.2  V.

Fig. 3. Time-dependent response of the device at zero bias with different wavelengths and irradiation intensities. (a), (d) 405 nm; (b), (e) 532 nm; (c), (f) 808 nm.

Fig. 4. Photoresponsivity (R) of the device with or without deposited Au NPs as a function of irradiance under different wavelengths with chopper frequency of 3944 Hz at a bias of 0 V: (a) 405 nm, (b) 532 nm, and (c) 808 nm.

Fig. 5. Time-dependent response of the device with or without deposited Au NPs as a function of irradiance under different wavelengths with chopper frequency of 3944 Hz at a bias of 0 V: (a) 405 nm, (b) 532 nm, and (c) 808 nm.

Fig. 6. (a) Structure diagram of FDTD simulation. The field distributions in the x–y plane under (b) 405 nm, (c) 532 nm, and (d) 808 nm light illumination.

Fig. 7. Electronic band structure and working principle of the CuInSe2 QD FEpTs with Au NPs.