Study On The Influence Of Source And Drain Electrode And Its Buffer Layer On The Performance Of Photosensitive Organic Field-effect Transistors

In recent decades,organic semiconductor materials have been widely used in the field of light detection due to excellent photoelectric properties.Because of the stability and field effect mobility and other factors that seriously restrict the performance of this type of device,the photosensitive organic field-effect transistor is not as fast as other kind of photosensitive organic devices as an important photodetector.Based on the existing deficiencies,the CuPc-based photosensitive organic field-effect transistor is optimized in this paper.The effects of different source and drain electrode materials and gate dielectric materials on device performance are compared,and the performance of the device is improved by optimizing the thickness of the electrode buffer layer.The conclusions reached in this paper are as follows.Firstly,the photosensitive organic field-effect transistor devices with Au and Ag as source and drain electrodes are introduced,and the performance parameters of the two devices are compared.Due to the difference of the work functions of the two metals,the mobility of gold electrode devices is 6.7 times of silver electrode devices under the same illumination conditions,and the performance parameters such as optical responsivity and maximum light-dark current ratio are much higher than silver.Then,the effect of the gate dielectric layer on the photosensitive organic field-effect-transistor was studied by using PVA and SiO₂ as the gate dielectric layers of the device.Experiments show that the SiO₂ gate dielectric layer device is significantly better than the PVA gate dielectric layer device in stability.However,the drain current of the PVA gate dielectric layer device is 10 times of the SiO₂ gate dielectric layer device under light conditions when Vg=-40V,Vd=-30V.In this paper,it is verified that the introduction of the electrode buffer layer can greatly improve the performance of the device by preparing 1nm thick MoO₃ as the electrode buffer layer in the device.Under the same illumination conditions,the electrode buffer layer device has a 3.7 times increase in optical responsivity compared to the electrodeless buffer layer device.In order to improve the performance of the device further,we prepared MoO₃ with a thickness of 1nm⁴0nm between the metal silver electrode and the organic functional layer,and optimized the thickness of the MoO₃ electrode buffer layer.The result shows that the optimal thickness of the MoO₃ electrode buffer layer is 15 nm.After optimization,the carrier mobility of the device is as high as 0.128 cm²/Vs,the threshold voltage is-0.7 V,the optical responsivity is 900.1 mA/W,and the maximum switching ratio is 5.6×10³.In addition,we prepared MoO₃ with a thickness of1nm-20nm between the metal aluminum electrode and the organic functional layer.The optimal thickness of MoO₃ is 5nm,the carrier mobility of the device is increased by 6.6 times,and the current switching ratio is increased by 6.5 times.