Carbon Nanotube Transistor with Colloidal Quantum Dot Photosensitive Gate for Ultrahigh External Quantum Efficiency Photodetector

PbS colloidal quantum dots (CQDs) are promising building block for developing the next-generation high-performance near-infrared (NIR) photodetector. However, due to the surface ligand isolation and surface defects, PbS CQDs usually suffer from low carrier mobility, which limits further optimization of PbS CQDs-based optoelectronic devices. Here, the combination of PbS CQD photodiode and carbon nanotube (CNT) film field-effect transistor (FET) achieves a transistorized NIR photodetector with a photosensitive gate. The photogenerated electrons are drifted to the dielectric surface by a negative gate electric field and built-in electric field, serving as an equivalent gate voltage to turn on the CNT FET, thus realizing the conversion of optical signals to electrical signals. The photodetector exhibits high performance, with a responsivity and detectivity of 41.9 A/W and 3.04 × 1011 Jones under 950 nm illumination, respectively. More importantly, the photodetector achieves an ultrahigh external quantum efficiency (EQE) of 5470% due to the CNT FET amplification function. Besides, the photodetector demonstrates a versatile photoresponse that allows for regulation of responsivity, detectivity, and EQE over a wide range through gate voltage control. The photodetector shows immense potential in NIR photodetection applications, and the distinctive structure of the optical module and electrical module separation also provides fresh thinking for the research and development of the next generation of optoelectronic devices.