The Effect Of The Nature Of Dielectric Surface On Electrical Properties Of DNTT Thin-film Transistors

Organic thin-film transistors?OTFTs?is one of the most basic units in organic electronics.OTFTs have attracted considerable attention in recent years for potential application in flexible electronics,such as wearable sensors,electronic skin,and conformable transparent displays,etc.Mobility is a crucial parameter for OTFTs that indicates the ability of carrier transport and can determine the switching speed,the strength and stability of output signals of devices.In OTFTs,there is an intensive dependence upon the nature of the dielectric surface for electrical performance of device because the charge-carrier transport generally takes place primarily at the first few molecular layers of the semiconductor/dielectric interface.The nature of dielectric surface not only affects the charge transfer,but also directly affects the growth of the vacuum-deposited semiconductor film.Therefore,the nature of dielectric surface plays a critical role in determining the OTFTs mobility.In this paper,we investigated the effect of the nature of dielectric surface on electrical properties of DNTT thin-film transistors,found the key effect factors of the OTFTs mobility and describe the mechanism.According to the mechanism,the nature of dielectric surface is purposefully modified to improve the quality of the semiconductor film and enhance the OTFTs performance.The main contents are as follows:1.The DNTT OTFTs were fabricated based on high-quality DNTT thin film by vacuum-deposition method.The optimal deposition condition can be obtained when the vacuum degree was 5×10^-4 Pa,the substrate temperature was 60?and the deposition rate was 0.1?s^-1.The DNTT OTFTs were fabricated on six kinds of dielectrics based on optimal deposition condition to study the effect of the nature of dielectric surface on devices mobility.The results show that the highest mobility(4.75 cm²V^-1s^-1)is obtained on the OTS/SiO₂ dielectric with the lowest adhesion energy.The adhesion energy was proven as the key factor affecting the OTFTs mobility.The lower adhesion energy,the larger grain size of semiconductor films,the higher quality of semiconductor films,the higher mobility of OTFTs.2.To verify the generality of the findings that the low adhesion energy between semiconductor and dielectric can improve mobility,the pentacene OTFTs were fabricated on four kinds of dielectrics with different adhesion energy.The highest mobility(1.16cm²V^-1s^-1)was obtained on the OTS/SiO₂ dielectric with lowest adhesion energy.The generality of the law of adhesion energy was successfully verified based on pentacene OTFTs.4.Based on the law of adhesion energy,the flexible c-PVA dielectric was purposefully modified by OTS modification.After the modification,the adhesion energy between semiconductor and dielectrics decreased from 81.92 mJ m^-2 to 44.33 mJ m^-2.With the decrease of adhesion energy,the OTFTs mobility was significantly improved,the average mobility increased from 0.13 cm²v^-1s^-1 to 1.96 cm²v^-1s^-1.Base on the law,the flexible DNTT OTFTs with high mobility was successfully fabricated on OTS/c-PVA dielectrics.