Investigation Of Photosensitive Field-effect Transistors And Photodiodes Based On Two-dimensional MoS₂/organic Semiconductor Heterojunction

Due to its unique advantages,such as large-area manufacturing,high light absorption coefficient,high luminous efficiency,good flexibility and low cost,etc.,organic semiconductor materials have a wide range of potential applications,such as electronic skin,radio frequency identification?RFID?and photoelectric detectors.In particular,organic semiconductor materials have better light absorption and higher extinction coefficient in visible and near-infrared light area,and the active layer of the photoelectric devices based on organic semiconductors can be far thinner,which can easily probe photosignal and significantly enhance the range of the incident angle.Based on the advantages of organic semiconductor materials,organic photosensitive diodes?OPD?and photosensitive organic field-effect transistors?Ph OFET?have a very bright prospect for development and application.Two-dimensional molybdenum disulfide?MoS₂?is one of the most attractive materials in two-dimensional semiconductor materials,owing to its unique optical,electronic,and mechanical properties.So far,although most researches focus on obtaining large-area,high quality monolayer MoS₂ and improving performance of inorganic electronic devices based on it,little research has been done on combining two-dimensional materials with organic semiconductor materials in application to photoelectric devices.This paper firstly summarizes the development of two-dimensional MoS₂ in recent years,and introduces the basic structures and the working principles of the Ph OFET and OPD,including the substrates,a variety of corresponding organic semiconductor materials and electrode materials of the devices.The following specific contents of the study are carried out on organic devices based on MoS₂/pentacene plane heterojunction:1.Two-dimensional MoS₂ is obtained through using chemical vapor deposition?CVD?method.The test results of X-ray photoemission spectroscopy?XPS?,Raman spectroscopy and absorption spectrum showed that the synthesized monolayer MoS₂ thin film is with high quality and good electronic structure.2.The Ph OFET device based on MoS₂/pentacene planar heterostructure was fabricated.Two-dimensional MoS₂ and pentacene were used for the channel layer and the photosensitive layer of the device,respectively.The device is illuminated to research its photoelectric properties.Results indicate that the Ph OFET based on MoS₂/pentacene plane heterojunction has excellent performance.Under 655 nm light illumination and at Vd = 50 V and Vg = 50 V,the photoresponsivity and external quantum efficiency of the device can reach about 103 A/W and 195% with an incident light power of 0.01 ?W,respectively,and the maximum photosensitivity can be up to about 1.8 × 10³ with an incident light power of 30.42 ?W.3.The OPD device based on MoS₂/pentacene plane heterojunction were fabricated.The effects of different top electrode materials?Au,Al?on the device performance were investigated.The experimental results have shown that compared to the device of the aluminum electrode,the device of the gold electrode is with more excellent performance due to the work function of gold electrode matching the HOMO energy level of pentacene.Under 655 nm light illumination and at the applied voltage of-15 V,the photoresponsivity and external quantum efficiency of the gold electrode device can reach about 0.31 A/W and 58.1% with an incident light power density of 0.015 m W/cm²,respectively,and the maximum photosensitivity can be up to about 9.1 × 10⁵ with an incident light power density of 27.821 m W/cm².