Organic Field-effect Transistors And Its Photosensitivity Based On PBDFTDTBT

Abstract:Because its structure is similar to BDT-based material, BDF-based material has attracted a lot of attention in recent years, but most of researchers focus it on the field of organic photovoltaic (OPV) with a photoelectric conversion efficiency (PCE) up to7%, none of them care about its OFET performance, and the performance is poor. This paper embarks from the preparation of high performance organic material, we synthesize a new BDF-based D-A structure conjugated polymer materials PBDFTDTBT by using the Stille coupling polymerization, the PCE of material can be6%. In view of its good performance in OPV, we prepare bottom gate top contact OFET by spin coating the material in solution as an active layer, and study its photosensitivity and lighting effect to the device. The results show that the materials both has excellent performance in OFET and OPT, at the same time the BDF-based semiconductor show its great potential in transistors in addition to the photovoltaic field. The detailed research content is as follows:First of all, the optical properties and morphology of material have been characterized. PBDFTDTBT has a wide range of absorption in300-800nm, conforming to its good performance in OPV. By modulating the surface of the substrate with OTS, we found that the surface roughness of the thin film is improved, and the effect of OTS to the film has been analyzed. On the basis we prepared OFET, it turns out the performance of OTS processing device is obviously superior to the untreated device, the mobility μ is improved an order of magnitude to0.05cm2/Vs, corresponding to the film morphology, illustrating the interface treatment is very important to OFET performance, and the mobility we get is highest in all BDF material reports.On the basis of the above, we study the transfer characteristic curve and output characteristic curve by illuminating the devices in different conditions. Varying the light intensity with1mw/cm2,5mw/cm2,50mw/cm2, and100mw/cm2, we find that the device has a certain threshold voltage drift as light intensity increases, from-15.6V to27.8V. That is because there is photovoltaic effect occurring in the channel under the light conditions, the stronger the light intensity, the more obvious photovoltaic effect. Device of the photocurrent gain also enhanced with light intensity increase, and the largest optical gain is as high as1.2×105in100mW/cm2. On the contrary, the largest photoresponsivity is360mA/W in1mW/cm2. In addition, the output characteristics are obvious linear and saturation region under illuminating, similar to traditional output characteristic. Since the accumulating holes by photovoltaic effect and gate electrode can influence the device simultaneously, there is a faint contact resistance under low Vds, hampering the device performance. Besides, the device shows good stability in air and light stability, no obvious degeneration is observed. All these results show that BDF-based materials have potential applications in OFETs and OPTs.