Organic Field Effect Transistor Memory Based On Organic Photochromic Materials

With the development of the information technology,people's demand for portable and wearable electronic devices is increasing.Among them,organic field effect transistor(OFET)memory,as an important component of future flexible devices,has become a research hot spot.Compared with traditional inorganic transistors,OFET memories have many advantages like much more simple fabrication process,higher flexibility and light weight.Organic photochromic materials undergo reversible structural changes under different light illuminations,which often accompany with changes in physical properties such as polarity,energy level and color.The introduction of photochromic material in OFET structure is supposed to achieve a certain optical response.In this paper,a photoresponsive OFET memory is fabricated by using organic photochromic material and polymer composite film as photosensitive layer and pentacene as channel layer.Specific work includes the following three parts:Firstly,the photoresponsive memory behaviors of OFET device are studied.The device is based on a highly doped silicon substrate with a 100-nm oxide layer,where PMMA-SP composite film is spin-coated and P-type organic semiconductor pentacene and upper copper electrodes are evaporated in turn.The experimental results show that there is no significant memory window in the transfer curve of the device testing under dark or visible light conditions.While,under the same intensity,ultraviolet light induces a large window(a positive VT shift).Even after removing the ultraviolet light,the photocurrent of device can still be maintained at a high level.The retention tests over 10000 s and more than 100 P/R/E/R cycles show that the device has good non-volatility and non-destructive readability.This OFET memory has a on/off ratio more than 106.Then,the factors affecting the optical storage of composite film devices are studied.In this paper,the factors affecting the optical storage characteristics of devices are studied one by one,and the specific effects of each factor on charge storage are found out through many experiments.These include the concentration of organic photochromic materials,programmed voltage,electret material and illumination condition.By studying the influence factors of charge storage,on the one hand,the device can be optimized under specific conditions,on the other hand,the device can be adapted to the specific needs of the environment through the selection of voltage or material.Based on the photoelectric charge storage behavior of the device and the energy level changes of two photoisomers of SP material,an energy band model of charge transition between the composite film and pentacene under photoelectric conditions is proposed.Finally,the application of ultraviolet dosimeter with composite film optical memory device is discussed.Based on the unique response of the composite film device to ultraviolet light,the linear relationship between the charge captured by the device and the exposure dose is obtained,and the S factor of the device is as high as 4.6×1010 mJ-1.Moreover,the device has little response to visible light,which can make the monitoring of ultraviolet light dose not be affected by long-band visible light.This indicates that the device has great potential in ultraviolet dose monitoring.It can be used as a dose warning device to avoid the damage to human skin and eyes caused by excessive ultraviolet radiation,which is of great significance in human health in the future.In this paper,the photoinduced charge storage behavior and mechanism of organic photochromic material-based OFET are studied.As a promising prospect,based on the particular photoelectric behavior of the device,the device application of ultraviolet dosimeter is realized.The experimental results show a hopeful research direction in the field of flexible optical storage and ultraviolet protection in the future.