Studies On Organic Field Effect Transistors Based On Conjugated Polymer Ultrathin Film And Their Ammonia Sensing Characteristics

In recent years,organic field-effect transistors(OFET)based on conjugated polymer ultrathin films have become a hot research direction in the field of gas sensing.Ultrathin films usually refer to films whose thickness is reduced to a few monolayers.The main advantage in the sensing field is that the ultrathin organic semiconductor layer can increase the physical contact area between the OFET conductive channel and the gas molecule,reduce the diffusion path of the gas molecule in the organic semiconductor,and improve the sensing performance of the OFET sensor device.This paper focused on the relationship between OFET ultrathin film structure and electrical and sensing performance,and aimed at optimizing the preparation process of ultrathin film OFET gas sensors and improving the sensing performance of OFET devices.The conjugated polymer ultrathin film was prepared in the blend system,the relationship between the ultrathin film microstructure and electrical and gas sensing properties was studied.Focusing on how to solve the contradiction between the sensitivity and electrical stability of the sensor device,the application of ultrathin film laminate structure in gas sensors was explored.The main contents of this paper are summarized as follows:(1)By adjusting the concentration of the polymer,a composite film with a vertical phase separation structure was obtained,and a series of ultrathin films with different thicknesses were obtained using a simple transfer-etching method.The phase separation method can be applied to the preparation of ultrathin film sensors.(2)Ammonia sensor based on ultrathin film OFET is prepared and the relationship between the film thickness and the ammonia sensing performance of the ultrathin film was studied.The OFET gas sensor based on PBIBDF-BT ultrathin film exhibits the best sensor performance with S=953,T_res=0.63±0.11 s,and T_rec=20.29±2.38 s.(3)Combining the phase separation method and the transfer-etching step to prepare an ultrathin film laminate structure OFET sensor.The ultrathin film laminate structure can effectively improve and stabilize the electrical performance of the sensor with the number of ultrathin film stacks increases.The hole mobility can maintain an upward trend and the maximum value is 0.58 cm²V^-1s^-1.It provides a new strategy for the preparation of OFET sensors with good electrical and ammonia gas sensing performance.(4)A high-performance organic transistor ammonia gas sensor with a laminated ultrathin film structure was prepared,and the electrical properties and the ammonia sensing transistor characteristics of ultrathin film laminated transistors were studied.It is proved that the stacking method based on solution phase separation can effectively control the electrical performance of OFET and ammonia gas sensing performance.Through the PBIBDF-BT ultrathin film stacking method,an OFET ammonia gas sensor with good performance was prepared under 10 ppm ammonia environment,with a mobility of 0.23 cm² V^-1 s^-1,the ammonia sensor performance of 90.7%.