Research Of Flexible Small-molecular Photoresponsive Organic Field-effect Transistors

In recent years,the photosensitive flexible organic field-effect transistors(OFETs)have attracted more and more attention and the application of flexible devices is becoming more and more popular.There are many advantages of flexible devices compared with the traditional rigid device,such as cost,light weight and flexibility and it has a widely application prospect in flexible display.At present,the OFETs fabricated on flexible substrates demonstrated comparable characteristics to the traditional amorphous silicon devices.But the development of flexible devices is still facing some problems,such as the poor flexibility and stability.In this work,we successfully fabricated the photoresponsive organic field-effect transistors(PhOFETs)on flexible polyethylene terephthalate(PET)substrates.By modifying the gate dielectric with octadecyltrichlorosilane(OTS),the device shows great stability which the current decline less than 4% after placing it in the chamber for 10 hours.Then,we bended the devices with different direction,different radius and different bending in the same radius.After all kinds of bending,we tested the device again,the results showed the performance of the device decreased significantly.After bending,the threshold voltage increased,the field effect mobility,the photoresponsivity and the photo current decreased.From this we can see,the devices become worse after bending.It is possible that the gradual loss of field effect of the device due to the fracture of the thin film during the bending process.In order to optimize the device performance,we fabricated the hybrid planar-bulk heterojunction flexible devices by using perylenetetracarboxylic dianhydride(PTCDA)and copper(II)phthalocyanine(CuPc)hybrid materials as the light absorption layer and using CuPc as the channel layer.We bended it in the same way,and the results showed light response decreased quickly which is similar as the single-layer device,but the change of mobility and threshold voltage are not significant.Therefore,we got a conclusion that compared to the single layer device,the optimized device shows a better electrical stability after bending.