Study On The Effect Of Nanowire Structure On The Performance Of Optoelectronic Devices In P3HT Thin Films

Polymer materials are widely used in the research and development of polymer thin film transistors and photodetectors because of their rich structure,good flexibility,solution processing,low cost and light weight.However,the disordered structure of polymer films limits the charge transport,so the preparation of highly ordered polymer films has become an important way to improve the charge transport of devices.The preparation of polymer films with nanowire structure is one of the important means to achieve this goal.However,the effect of this structure on charge transfer and device performance needs to be further explored.At the same time,there are few reports on the influence of nanowire structure on the performance of photoelectric devices such as electrochemical transistors and photodetectors.In this paper,P3HT solution containing high ordered nanowire structure was prepared by water bath assisted anti solvent method,and applied to transistors,electrochemical devices and photodetectors,which significantly improved the device performance.At the same time,the effects of nanowire structure on charge transfer performance,electrochemical doping and luminescence performance were discussed.The main results are as follows:1.P3HT thin film field effect transistor（PFET）and electrochemical transistor（PECT） with nanowire structure were prepared.In PFET,the mobility of devices with nanowire structure reaches 2.82×10^-2 cm²v^-1s^-1,which is 60 times higher than that of disordered thin film devices,but the threshold voltage is 20%higher than that of the latter.The introduction of nanowire structure is the main reason for the improvement of device mobility.It is found that there are a large number of deep traps between nanowires,which may be the reason for the increase of threshold voltage.In PECT,the nanowire structure improves the overall performance of the device.At the same time,it is found that the surface of J aggregation region（i.e.nanowire region）is preferentially doped in the nanowire film,which indicates that the internal charge of the device is mainly transmitted through nanowires.In addition,electroluminescent transistors were prepared.The results showed that driven by-4 V source drain voltage,the transistor lost its regulation performance due to deep electrochemical doping.At the same time,P3HT thin film realized electroluminescence,and the device became a polymer electroluminescent electrochemical cell.In this device,nanowire structure can significantly improve the luminous efficiency and stability of the device.Unlike non Nanowire Films,doping and luminescence occur in the same region.It is difficult to dope the interior of nanowires in nanowire films,which avoids the luminescence quenching caused by excessive doping,so as to better retain the luminescence properties of polymers in nanowires.2.P3HT:PC₆₁BM thin film photovoltaic photodetector with nanowire structure was prepared.Under the working voltage of-0.5 V,the dark current density of the device is5.67×10^-5 m A/cm²,which is nearly 4 orders of magnitude lower than that of disordered thin film devices,and the light dark current ratio is increased to 1.59×10⁵,specific detection rate from 2.71×10¹⁰ Jones increased to 1.50×10¹² Jones.The linear dynamic range is increased from 69.3 d B to 133.8 d B under 625 nm monochromatic light;From74.0 d B to 138.5 d B under 523 nm monochromatic light;From 77.8 d B to 144.2 d B under400 nm monochromatic light.X-ray photoelectron spectroscopy（XPS）test and oxygen plasma etching active layer absorption spectrum test show that the introduction of nanowire structure enriches PC₆₁BM to Al electrode and P3HT to ITO electrode.This gradient structure can significantly reduce the dark current.In addition,the edge on orientation of P3HT nanowires will also reduce the dark current of the device.3.P3HT:PC₆₁BM thin film photoconductive photodetector with nanowire structure was prepared.Compared with disordered thin film devices,the dark current density decreases from 0.02 m A/cm² to 2.25×10^-5m A/cm² at-0.5 V working voltage,the light dark current ratio reaches,which is nearly three orders of magnitude higher than that of disordered thin film devices,and the specific detection rate reaches 1.90×10¹³ Jones。More importantly,the nanowire structure increases the linear dynamic range of the device from 41.7 d B to 147.4 d B under 625 nm monochromatic light;From 36.8 d B to 133.2 d B under 523 nm monochromatic light;From 38.5 d B to 160.1 d B under 400 nm monochromatic light.The continuity and cycle switching tests show that the device can work stably and repeatedly.In addition,Sn O₂ was used instead of Zn O as the modified layer,and similar performance results were obtained.This shows that the nanowire structure has universality in improving the performance of polymer photoconductive detector.