| As organic molecules,organic semiconductors have many active sites or groups in their structures,which makes them have unique advantages in basic research and application research.In basic research,a large number of organic semiconductors with excellent photoelectric properties have been synthesized.However,because the synthesis process of asymmetric conjugated molecules is easy to control,most of organic semiconductors which have high performance are based on symmetric conjugated structure,the research on asymmetric conjugated molecules is relatively backward.This condition also exists in derivatives of anthracene,which the number and properties of their derivatives with asymmetric structures are far below those of symmetric structures.The comparative study of symmetric and asymmetric structures in organic semiconductors helps to understand the carrier transport mechanism,synthesize high-performance organic semiconductors.In application research,organic semiconductors have many functional groups which cause many interactions with other organic molecules,so they can be used in chemical sensors.The sensor based on OFETs has the advantages of mechanical flexibility,biocompatibility,low temperature solution process and light weight,which makes it an ideal choice for real-time field detection.Organophosphorus pesticides excessive use poses a serious threat to the ecological environment and human health.The traditional methods of pesticide detection are mainly based on chromatography and mass spectrometry.However,due to the need of large,expensive instruments and complex sample preparation process,it is unable to achieve fast,real-time,efficient detection.Based on the above background,this paper studies the basic properties and applications of organic small molecular semiconductors on the basis of the organic field-effect transistors.1.Two anthracene derivatives with an asymmetric structure,2-phvA and 2-pheA,were synthesized using anthracene molecules as the framework.The two materials were characterized by UV,CV,and TGA with 2-phA previously reported to determine their energy level and thermal stability.Organic thin-film and single-crystal organic field-effect transistor devices based on three materials were prepared.The field-effect performance of three devices was characterized and the carrier transport mode in organic semiconductors was studied by the dependence of device mobility on temperature.The experimental results show that the 2-phvA single crystal device has the highest mobility among the three materials,which is also higher than its corresponding symmetrical anthracene derivative,reaching 10 cm2 V-1 s-1,which is also the highest value of asymmetric anthracene derivatives,and two kinds of carrier transport modes were found in the temperature-variation experiments,band-like transport mode and transition transport mode.The activation energy as low as 8.03 meV has been found in transition transport mode.The single crystal analysis results show that the 2-phv molecular stacking mode is fish-bone-shaped,and the molecules grow perpendicular to the substrate.2.A sensor based on MMC-OFETs were prepared to detected dimethoate which was an organophosphorus pesticide.The detection results showed that the monolayer molecular crystal showed ultra-high sensitivity to dimethoate and the sensor has fast response/recovery time in 20 s/68 s.The detection limit was as low as 0.60 ppb,which is the lowest detectable concentration of dimethoate reported so far,far lower than the daily allowable dose of human body.Responsivity of OFETs sensors based on monolayer molecular crystals is significantly higher than OFETs sensors with multi-layer crystals at different concentrations of dimethoate vapor.There is obvious selectivity of MMC-OFETs sensor for dimethoate vapor compared with several different gases and other organophosphorus pesticides.In addition,the sensor based on flexible substrate has good stability and sensing performance under different bending degrees. |
PDF Full Text Request