Research On The High-performance Dielectric Layer In Organic Field-effect Transistor

With the coming of flexible electronics era,organic field-effect transistor(OFET)have drawn a lot of attention by virtue of its unique characteristics.Under the continues effort of researchers,the mobility of organic semiconductor has been comparable to that of polycrystalline silicon(>10 cm~2/Vs),and it has huge potential in the area of flexible electronics.However,the operation voltages of almost reported high-performance OFET were relatively high which hardly satisfy the energy consumption requirement of portable devices.As the key element of dominating operation voltage,novel fabrication method and surface modification of high-performance dielectric layer become our research focus to improve OFET's performance and decrease the energy consumption.1,Developing a novel solution precursor conversion method to fabricate ultrathin silica dielectric layer.The solution precursor was spin-coated and activated by heat,and then,ultrathin silica film was obtained.This method is suitable for large-area,low-cost production,and the obtained film exhibits low leakage current density,high capacitance and ultra-flat surface.Both p-type and n-type OFETs based on this ultrathin silica film got high electrical performance under low operation voltage(3?4 V).2,Researching the influence of different area density of octadecyltrichlorosilane(ODTS)which is modified on silica's surface on crystallization of organic semiconductor and OFET's electrical performance.The results of experiments reveal that the major effect of ODTS is to improve the crystallization conditions of organic semiconductor.High area density of ODTS is beneficial to get highly uniform and ordered grain and closely packed semiconductor film,meanwhile,higher mobility.However,the device's performance is also affected by the roughness of dielectric layer surface and the interface compatibility between semiconductor and dielectric layer.3,To explore the difference of influence on semiconductor's crystallization and OFET's performance,we compared polymer CYTOP and ODTS modified on silica's surface.We found that the CYTOP surface have higher mean square roughness and bigger contact angle than ODTS.The larger sized DNTT grains can be grown on the surface of CYTOP,showing a"stand-up"lamellar shape,but with larger crystal gaps.In contrast,DNTT grown on the surface of ODTS has smaller crystal grains but more closely packed particles.Under the combined influence of surface roughness and dielectric constant of CYTOP,and the grain gap of DNTT,the performance of CYTOP-based device is slightly worse in mobility but better in threshold voltage and subthreshold slope.This shows that the modification effect of the CYTOP layer mainly acts on reducing the number of defects on interface between organic semiconductor and dielectric layer,so that the potential trap density which will capture charge in conductive channel is greatly reduced.