A PbSe nanocrystal vertical phototransistor with graphene electrode

Recently, low-voltage phototransistors have become promising candidates for optoelectronic applications. In this study, a general strategy for the fabrication of high-performance lead selenide (PbSe) nanocrystal (NCs)-based vertical phototransistor (VPT) using graphene as electrode was presented. Within the vertical geometry, channel length was determined by measuring the thickness of NCs thin film, thus enabling the device with ultrashort channel length (213 nm) without expensive lithography. Moreover, a high current density of 863 A cm(-2) was obtained at low voltage. Utilizing the unique tunable Fermi energy (FE) of graphene, the vertical carrier transport could be effectively modulated by the Schottky barrier height between the graphene and PbSe NCs active material. As a result, the device exhibited excellent photoelectric characteristics, including a responsivity of 1.1 x 10(4) A W-1, an external quantum efficiency of 1.7 x 10(6)% a detectivity of 1.3 x 10(10) Jones, and a temporal response of 7 ms at an illumination irradiance of 36 mW cm(-2). Through analysis of energy levels, the carrier transport was modulated by the barrier height at the graphene-PbSe NCs interface, which is attributed to the tunable FE of graphene. Fabrication of VPT with high performance and low energy consumption represents a significant step forward for high-speed opticalswitch applications and future nanoscale complementary circuits.