High performance PbSe colloidal quantum dot vertical field effect phototransistors

Here, vertical field effect phototransistors (VFEPTs) based on lead selenide colloidal quantum dots (PbSe CQDs) for infrared photo detection were investigated, using Au/Ag nanowires as the source transparent electrode. VFEPTs have the advantage of easy fabrication of ultrashort channel length devices, as the channel length is simply determined here by the PbSe CQDs active layer's thickness (260 nm). In ultrashort channels, photo-excited carriers quickly (in nanoseconds) transfer to the drain. As soon as a hole (electron) reaches the drain, a hole (electron) is replenished from the source. Accordingly, multiple holes circulate in the ultrashort channel following a single electron–hole photo generation. As a result, the device exhibits superior photoconductive properties over the lateral structure. PbSe CQD VFEPTs show ambipolar operation under low voltage down to one volt at room temperature. Moreover, high photo responsivity and high specific detectivity of 2 × 10⁴ A W⁻¹ and 7 × 10¹² Jones are also achieved in the devices under 808 nm laser illumination. The transparent electrode-based near infrared VFEPTs prepared through this self-assembly solution process show promise for applications in electronics and photoelectronics. (paper)