Preparation And Gas Sensing Characteristics Of PbPc Organic Thin-film Transistors

Along with the increasingly severe atmospheric environment around us,in order to realize the accurate detection of poisonous and harmful gas,gas sensor research and development have become extremely important,sensitive material is the key to gain high performance.Phthalocyanine material?MPc?has wide application as sensitive layer in gas sensor.This thesis about the experimentation which used the organic small molecular semiconductor material PbPc as the active layer,refer to OLED the multifunctional and multivariate coating system,adopted the magnetron sputtering process and vacuum thermal evaporation process,to prepared the organic thin film transistor with vertical structure.the structure of diode is MgAl/PbPc/Cu,and Cu used as anode,MgAl used as cathode,they were all for the test called the gas sensing properties of PbPc thin film diode.The structure of triode is Cu/PbPc/MgAl/PbPc/Cu,it was for the test called the basic electrical characteristics of OTFTs.By using the self-made measurement system for gas sensitivity and Keithley 4200scs semiconductor characterization system,tested with the gas sensing properties of PbPc Thin film transistor to NO₂.And through the further theoretical analysis to the measured data of I-V characteristic,compared the sensitivity degree of device to those different concentrations NO₂gas.The research results shows:the MgAl/PbPc/Cu thin film transistor with good schottky diode characteristics,when organic thin film adsorbent the NO₂gas,it will reacted The reduction reaction,according to the gas sensing mechanism of phthalocyanine material,the reducing gas used as electronic donor will produce a good effects of donor doping,leading to the changing of concentration with the PbPc film carrier,so the doping with the reducing gas reduce the number of carrier inside the film,which made the conductivity of the phthalocyanine material reduced.Put the device in 10^-55 NO₂ gas and last about74minutes,then the forward current will reduce almost 65 times.And the schottky barrier height of MgAl/PbPc will rose up about 20meV.At the same time,owing to the growing number of the adsorbed gas NO₂ PbPc film carrier,the reverse current of device grows nearly 4 times,indicating that the PbPc organic thin film transistor has significant sensitive characteristics to the NO₂ gas.Analysis the I-V characteristics of Cu/PbPc/MgAl/PbPc/Cu organic thin film transistor,the I_ecc current between emitter and collector will reduce with the growing of the base voltage V_b,the device has the unsaturated characteristic.