Study On Performance Optimization And Gas Sensitivity Of Perylene Imide Heterojunction OTFT

Organic thin film transistor（OTFT）have great application value in the fields of ac-tive drive arrays,organic logic devices,radio frequency tags and sensing,improving its comprehensive performance to promote practicality is the focus of current research.In this paper,the formation mechanism and accumulation effects of organic pn-heterojunction are studied.Perylene diimides heterojunctions are used to increase the free carrier concentra-tion of the active layer,and the crystalline quality of the active layer is improved by opti-mizing the insulator layer.In addition,gas sensing of perylene imide derivative films to hydrazine hydrate is explored.Firstly,the role of organic heterojunction charge accumulation effect in OTFT is studied.The discontinuous accumulated heterojunction is prepared by using copper phthalocyanine(F₁₆Cu Pc)and pentacene,and the doping effect of the heterojunction at the channel and the enhanced electrode injection effect are compared.Based on the organ-ic-organic interface energy level alignment theory,the Lowest Unoccupied Molecular Or-bital(E_LUMO)of F₁₆Cu Pc is pinned to the pentacene Fermi level（E_F）,which theoretically proves that the carrier concentration at both sides of pn-heterojunction is significantly in-creased.Based on the dual optimization of channel doping and enhanced electrode injec-tion,the performance of pentacene OTFT has been greatly improvedSecondly,we study the formation mechanism of organic pn-heterojunction and de-termined that the interface barrier is beneficial to form accumulated heterojunction.We combine with the interface barrier and the E_F difference between the p-type and n-type materials to establish a theoretical model in OTFT.2nm PDI and its derivatives PDI-1/PDI-2 are used as discontinuous thin films to modify pentacene OTFT.Along with the E_LUMO of n-type materials decreasing,the E_F difference of the materials at both sides of the heterojunction further increases and the carrier accumulation effect at both sides is further enhanced under the joint effect of the interface barrier,the free carrier concentra-tion is significantly improved.Thereby the performance of transistors are effectively op-timized,and we can control the OTFT from the enhancement-mode to the depletion-mode.Again,we analyze the formation conditions of pn-heterojunction.By controlling PDI-3 film thickness and deposition rate,we establish the relationship between deposition rate and grain size,accumulation effect,and determine the optimal thickness.The applica-tion of pentacene as the discontinuous modified layer and PDI-3 as the active layer con-stitutes heterojunction OTFT,whose performance is significantly improved compared with the pristine PDI-3 device.In addition,we apply the composite insulator layer to improves OTFT performance.Copper phthalocyanine（Cu Pc）OTFT was prepared based on composite insulator layer composed of polyvinyl alcohol and polymethyl methacrylate/polyglycidyl methacrylate.The use of two organic polymer materials complement each other to improve the overall performance of the composite insulator layer:high dielectric constant（6.0）,hydrophobi-city,ultra-smooth surface（1.47（?））.The crystal quality of the Cu Pc film is effectively im-proved.Compared with the single insulator layer device of the same thickness,the per-formance of the composite insulator layer device is significantly improved.Finally,we explore the gas-sensitive sensing of peryleneimide（PDI-4）film to hydra-zine hydrate.We deposit the PDI-4 on the end surface of the optical fiber,establish the relationship between the hydrazine vapor concentration and the refractive index of the sensitive film,increase the fiber cross-sectional area ingeniously to improve the quality of the film deposition,and develop a dual parameter sensor to detect the concentration of hy-drazine vapor and temperature.The gas sensor has excellent performance,and has the ad-vantages of full optical system,small size,good repeatability and high reliability.