Research On Photoelectric Detector Based On Organic Field Effect Transistor

The advent,research and application of semiconductor materials and devices have greatly promoted the progress of social productivity,and have also brought tremendous changes to people's production and life.With the continuous development of science and technology,the inorganic semiconductor devices made of semiconductor silicon,germanium and other materials have gradually emerged from the disadvantages of production,cost and products.In this case,the research on organic semiconductor materials came into being.The emergence of organic semiconductor materials is of great significance to the realization of miniaturization,mass production,flexibility and low cost of devices.After being found to have photosensitive properties,it has attracted great attention worldwide.Organic semiconductor materials have been widely used in photodetectors through more than 20 years of research and development.A photodetector is a semiconductor device that converts an optical signal into an electrical signal.It can be used for light detection,light control switches,and image sensors.The photodetector with organic field effect transistor structure has very good light response characteristics and electrical characteristics.It is a novel photodetector with great potential.In this thesis,the development of photodetectors and the current research status,principles and performance parameters at home and abroad are briefly described;the structure,working principle,material technology and other aspects of organic field effect transistors are introduced in more detail,Focusing on the following aspects:?1?Research and design the technology of pentacene field effect transistor.An organic field effect transistor device with a top gate bottom contact structure is prepared.The experience use pentacene with a purity greater than 99%as the semiconductor active layer material,use poly methyl methacrylate?PMMA?with excellent light transmission effect and simple process as the dielectric layer,and use chlorobenzene as the PMMA solvent.An insulating layer with a thickness of 510nm was prepared on the surface of ITO glass by the solution spin coating method.By vacuum evaporation method,the experience prepared pentacene thin film with active layer thickness of 35nm and 50nm and Au source-drain electrode.?2?After the preparation is completed,the test is performed,and the variation of device parameters under different active layer thicknesses is analyzed.In a dark environment,devices with active layer thicknesses of 35nm and 50nm were tested separately.By testing the output characteristic curve of the device.Both devices show good field effect characteristics.The maximum leakage current of the device with a film thickness of 50nm is 15.3?A,while that of a device with 35nm is only 9.9?A.After that,the experience keep the V_DS and V_GSS constant at-50V and test the transfer characteristic curve.The threshold voltage of the 35nm device is-19.73V,and the threshold voltage of the 50nm device is about-16.01V.The device migrations were 3.98×10^-2cm²/V?s and 4.98×10^-2cm²/V?s respectively.By comparison,the experience found that the device with a film thickness of 50nm showed better electrical performance.?3?For further analysis,the experience selected a device with a thickness of 50nm for electrical performance testing after illumination,the properties of the pentacene film,and the photosensitivity based on the photodetection of the pentacene field-effect transistor.As a result,pentacene field-effect transistors exhibit good photoelectric characteristics.At this time,pentacene field-effect transistors can be used as photodetectors.Experiments have shown that the photodetector can respond to light in the range of 300?750nm,with a response of up to123.7mA/W.The maximum light/dark current is 5×10⁵.Through the absorption spectrum test?XDR?film in the ultraviolet-visible absorption-near infrared region,a high absorption peak appeared at 666nm.It shows that the device has better absorption effect on red light.Observing the AFM picture of the surface layer of the film,it is found that the pentacene crystals are tightly crystallized with high flatness and uniform crystal size.The roughness is only 6.3nm.The photoresponse time characteristic test results are good.The photocurrent rise time of the photodetector based on pentacene field effect transistor is about 0.31ms,and the fall time is about 0.3ms.Finally,the experience conducted a stability test in air to prove that it has better stability in oxygen and water vapor.