[ Instrument Network Instrument Development ] Effectively regulating and balancing the separation, transmission and recombination of photogenerated carriers is essential for achieving highly sensitive photodetectors. Conventional organic phototransistors are mostly based on a single layer heterojunction or bulk heterojunction structure. In the former, the donor and acceptor are respectively formed in a layered film superposition. In the latter, the donor and acceptor materials are blended to form photoelectric conversion activity. Floor. Although the above structures provide superior photodetection performance, they are difficult to simultaneously consider the efficient separation and transmission of photogenerated excitons and the low exciton recombination rate, which severely limits the further improvement of the photodetection performance of the phototransistor.
Composite layered phototransistor structure diagram and energy level distribution diagram
In order to solve the above problems, researchers from the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences proposed a novel composite layered phototransistor structure consisting of a C8-BTBT channel layer for efficient carrier transport and an efficient C8- BTBT: PC61BM bulk heterojunction photoactive layer and the composition of the ultra-thin MoO3 hole transport layer between them (Fig. 1). The excitons generated in the photoactive layer are effectively separated at the bulk heterojunction, the generated electrons are captured by the acceptor PC61BM (CTE effect), and the holes are injected into the channel layer, and the inorganic MoO3 can further promote the injection of holes. The electrons are blocked, thereby effectively suppressing electron-hole recombination. Furthermore, the C8-BTBT channel layer with high mobility provides an unimpeded "highway" for the transport of holes, which are transported freely and at high speed in the channel. Therefore, through the ingenious design and optimization of the generation, separation, transmission and composite suppression of photogenerated excitons, the photodetection performance of the phototransistor is greatly improved, and the photosensitivity (Ilight/Idark) reaches 2.9'106. The photoresponsivity reached 8.6'103 A/W, the Detectivity was 3.4'1014 Jones, and under low light (32 μW/cm2), the external quantum efficiency was 3 × 106%.
Moreover, at the device application level, the research team used this novel structure to fabricate flexible photodetector devices, and verified the reliability of the structure in flexible devices through bending experiments. At the same time, the research team also prepared an array structure of phototransistors to verify its superior potential in photo imaging applications.
The design of the device structure proposed in this work has laid a new path to high-performance organic phototransistors. In order to achieve high performance (flexible) photodetectors and optical imaging devices, important design ideas and implementation methods are provided. Moreover, this structure has excellent universal applicability, providing a new study for the electronic and optoelectronic principle exploration and device application development of high-performance photodetectors and other related organic optoelectronic devices from the ultraviolet to the near-infrared wide spectral range. platform.
The research results were published in Advanced Materials. The research was funded by the Guangdong Science and Technology Plan Project and the Shenzhen Science and Technology Plan Project.
(Original title: Shenzhen Advanced Institute successfully developed ultra-sensitive photodetectors)
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