Organic Thin Film Transistor And Its Gas Sensing Characteristics Based On Polymer Blend System

Organic thin-film transistor?OTFT?,as one of the fundamental organic electronic components,has various significant advantages including extensive material sources,facile fabrication techniques,and compatible with flexible and large-area substrates.Thus,in recent years,OTFT has attracted widespread research attention in the field of flexible integrated circuits,physical/chemical sensors,wearable devices and so on.With the advance of field-effect mobility,the electrical performance of OTFT has already been qualified to meet various application requirements,so the current research focus is gradually shifting from optimizing of device performance towards exploring functional applications.Among them,OTFT-based gas sensor has tremendous application prospects in the hazardous gas monitoring and intelligent healthcare due to the additional advantages incorporating flexible design of sensitive materials,signal amplification,and multi-parameter monitoring.In the previous studies,the researchers attempted to improve the gas sensing performance mainly via the modification of chemical structure,regulation of film morphology,and interface engineering.However,most of the sensing layers in OTFT are composed of single organic sensitive material,which significantly limits the intrinsic gas sensing response.Herein,for the first time,we introduce the approach of blending semiconducting polymer/conjugated high-bandgap polymer into the OTFT-based gas sensor to study the effect of blend system on both the electrical and gas sensing performance.The main content of this thesis consists of three parts as follow.1.Based on the poly?3-hexylthiophene??P3HT?/poly?9-vinylcarbazole??PVK?blend system,through adjusting the blend ratio,we find when the weight ratio is 1:1,as compared to the pure P3HT device,the gas responsivity of the blend device to nitrogen dioxide?NO₂?improves most significantly at the whole analyte concentrations,and the material cost decreases to one-eighth.Moreover,this blend device also possesses good working stability,repeatability,low power consumption,and gas selectivity.2.Basedonthepoly?3-hexylthiophene??P3HT?/poly[N,N?-bis?4-butylphenyl?-N,N?-bis?phenyl?benzidine]?poly-TPD?blend system,we find that with the increase of poly-TPD weight fractions,the NO₂ responsivity of the blend devices enhances gradually at the whole analyte concentrations.When the weight fraction of poly-TPD is 90%,the enhancement comes to the maximum and realizes the limit of detection of 242.6 ppb.Meanwhile,the blend devices also have benign gas selectivity and environmental stability.3.In those two blend systems,we find that the sensing performance can be further improved when the gate voltage switches from-40 V to 0 V,which also significantly reduces the power consumption.Finally,from two theoretical viewpoints of multiple trapping and release model and channel thickness dependence on gate voltage,we analyze the underlying gas sensing mechanism.In summary,we studied the effect of polymer blend system on both the electrical and sensing performance of the OTFT and further the regulation of gate voltage on the gas responsivity.This work will provide novel ideas to the material choice,low-voltage operation,and performance optimization in the field of OTFT-based gas sensor.