Study On Preparation And Photoelectric Properties Of Flexible And Low-voltage Organic Phototransistors

Low-voltage organic phototransistors have attracted considerable research attention due to their potential application for low-cost,flexible,and wearable electronics.In order to obtain good photosensitivity,high-performance organic semiconductors,controlled morphology of active-layer,and complicated fabrication processes can be needed for the fabrication of the devices.The use of these methods increases the difficulty of device fabrication,and therefore,improving the photosensitivity of OPTs via new strategies is necessary.The charge trapping effect is generally thought to have a potential impact on the performance of the transistors;however,this effect can be applied to improve the photosensitivity of OPTs.Single – component,flexible,and low-voltage OPTs was fabricated using narrow band–gap conjugated polymer as the active layer in this paper.Insulation layers with different trap states were prepared by regulating the physical and chemical properties of monolayers,and explored the effects of different insulating layer/semiconductor interface on photoresponse performance of the transistors.The main work of this paper is as follows:?1?The surface interface engineering was used to assemble the phosphoric acid monolayer on the surface of the alumina insulating layer via different growth times,and different trapped insulating/semiconductor interfaces were prepared.Flexible and low-voltage OPT were fabricated based on an isoindigo conjugated polymer PBIBDF-BT,the device is capable of operating at 5 V with a maximum mobility of 5.03 × 10^-2 cm²V^-1s^-1,a threshold voltage of 1.87 V,and a maximum on/off ratio of 5.25 × 10⁵.The effects of different interfaces on the morphology of semiconductor thin films and the photoelectric properties of devices were also investigated,and the results showed that the mobility of the device decreases with the increase of the interface trap density.However,the photoresponse of the device improves due to the existence of the interface trap state.?2?In order to explore the effect of interface charge-trapping effect on the photosensitivity of the device,using a monolayer that grows for 12 hours as insulating layer,the NIR photoresponse of n-type PBIBDF-BT OPTs was investigated.The OPTs exhibit good photosensitivity to 980 nm NIR with the photocurrent/dark-current ratio?P?and photoresponsivity?R?as high as 5 × 10³ and 20 m A/W,respectively,and the OPTs also present a fast optical switching speed of 20 ms and excellent mechanical flexibility.The photosensitivity of PBIBDF-BT OPTs?SAM – 12 h?was successfully enhanced by taking advantage of the interface charge-trapping effect,which promoted the separation and transmission of photogenerated electron/hole pairs and produced higher photocurrent.?3?Phosphoric acid monolayers?C₆N₃?with different chemical end groups were synthesized and used to modify alumina insulating layers.Single-component high-performance low-voltage phototransistors were fabricated based on pyrrolopyrroledione derivative?DPP-DTT?.The device is capable of operating at -6 V with a maximum mobility of 0.189 cm²V?-1?s^-1.The new OPTs based on Al O_x/C₆N₃ hybrid insulating layer exhibit good photosensitivity to 808 nm NIR with the photocurrent/dark-current ratio?P?and photoresponsivity?R?as high as 2.2 × 10⁴ and 104 m A/W,respectively.