Fig. 4
Electrical and photoelectrical characteristics of the crystals. a Bird’s-eye view of a schematic configuration of the photodetector based on a 2D organic crystal, and the molecular structures of p-MSB, perylene, and α-6T. b Transfer (drain current (Id) vs. gate voltage (Vg), when drain voltage (Vd) is −80 V) and c output (Id vs. Vd) curves of a typical 2D p-MSB device. The inset of b is the optical microscopy image of a 2D p-MSB device. d Transfer curves of the device (Vd = −80 V) in the dark or under 254-nm illumination with different power intensities. e On-state (Vg = −80 V) and off-state (Vg = −20 V) Id versus Vd curves of the p-MSB device in the dark or under 254-nm illumination (43.1 μW cm−2). f, h External photoresponsivity (Rex) and g, i, internal photoresponsivity (Rin) as a function of the number of molecular layers (p-MSB, perylene, or α-6T) under illumination (12.5 μW cm−2 254 nm, 14.1 μW cm−2 365 nm, 112 μW cm−2 405 nm, and 141 μW cm−2 420 nm) when the devices operate in the ON-state (f, g) or OFF-state (h, i). The dashed lines in g and i indicate different 2D limit effects on the Rin when the crystal is located on different substrates (SiO2/Si or h-BN). The scale bar in b is 20 μm
