| Organic photoelectric field effect transistor（OPE-FET）is photodetector that uses organic semiconductor as active layer and operates based on the FET principle.It can efficiently convert external optical signal into electrical signal.Based on the advantages of organic semiconductor such as excellent mechanical flexibility,low temperature and large area fabrication,and the internal gain characteristics of FET,OPE-FET has a very broad application prospect.Due to the capacitive structure of OPE-FET,carriers accumulate on the insulating layer and semiconductor interface,forming the channel for carrier transportation.Therefore,interface modification has an important impact on device performance.Based on PBDB-T:ITIC-TH organic semiconductor active layer,OPE-FET devices are prepared by modified the insulating layer and semiconductor interface.A platform is designed and built to explore the mechanism of interface influence on device performance.The specific content includes:The effects of active layer film thickness and interface modification on device performance were studied.In OPE-FET devices,the active layer thin film serves as both a photosensitive layer and a semiconductor channel.Therefore,the thickness of the thin film has a very important impact on device performance.In this paper,we first deposited active layer films with different thicknesses on the substrate by varying the concentration of the active layer solution.The structure and properties were characterized.The results show that the device prepared with 10 mg/m L of active layer solution has the best performance,with a maximum optical response of 7.169 A/W,an optimal external quantum efficiency of 1169.48%,and a maximum specific detectivity of 2.777×1012Jones,gate voltage is+54 V.Based on film characterization,it indicates that interface traps have a significant impact on device performance.Because interface traps can be modified by groups,organic material with different polar groups（polymethyl methacrylate,polystyrene,and octadecyltrichlorosilane）are selected to modify the semiconductor and insulating layer interfaces.The test results show that the best performance is octadecyltrichlorosilane interface layer modified device,the highest optical response of 24.17 A/W,the highest external quantum efficiency of 10199%,and the highest specific detectivity of 4.09×1013 Jones,gate voltage is+15.5 V.Secondly,the influence of high dielectric constant dielectric layers on device performance was studied.The gate voltage gap in the field effect on and off state is broad,which can cause adverse effects such as high power consumption in practical applications.Therefore,the research on reducing the gate voltage difference in the field effect on and off state of devices is of great significance.In this paper,we use hafnium oxide and chitosan dielectric layers with high dielectric constants to prepare OPE-FET devices and study their photoelectric properties.The results show that the chitosan dielectric layer device prepared by the drop coating method has good performance,with a significant decrease in operating voltage compared to the silicon oxide dielectric layer device.The device has a maximum optical response of 3.115 A/W,a maximum external quantum efficiency of 482.772%,and a maximum specific detectivity of 1.149×1012 Jones,gate voltage is-2.5 V.The research in this paper shows that the dielectric and interface layers of OPE-FET have a significant impact on the threshold voltage and operating voltage of devices.Further research is of great significance for the development of photodetectors and logic circuits. |
