Research On Near Infrared Organic Photodetectors And Imaging

Near infrared organic photodetectors are widely used in military reconnaissance and medical imaging.Electron transport layer plays a role in blocking holes and transporting electrons in organic photodetectors.ZnO nanoparticles have been widely used in near-infrared organic photodetectors due to their high transmittance,stable properties and solution-prepared characteristics.Improving the film forming quality of ZnO nanoparticles can effectively reduce the dark current of devices and improve the performance of devices.In this thesis,the near infrared organic photodetector was prepared by using ZnO nanoparticles as the electron transport layer of the device.The influence of particle concentration on film forming quality and device performance was explored.On this basis,the flexible organic photodetector was prepared and used for heart rate detection.In addition,a near-infrared organic upconversion device is prepared and used for biological imaging.The imaging results are analyzed and enhanced by digital image processing technology.The main research contents of this paper are as follows:（1）By changing the dilution ratio of ZnO nanoparticles,the particle concentrations of 6.44 mol/L,1.49 mol/L,0.84 mol/L and 0.58 mol/L ZnO nanoparticles were prepared,and the electron transport layer was prepared and characterized by the solution.It is found that at high concentration,the particle agglomeration phenomenon in ZnO nanoparticle solution is relatively serious,the existence of agglomeration groups seriously affects the film quality of the electron transport layer,resulting in poor film uniformity and density,and high dark current density of devices.When the ZnO nanoparticles were diluted with ethanol at a ratio of 1:4,the particle concentration was reduced to 0.84 mol/L,and there were no clusters on the surface of the films.Compared with the undiluted devices,the dark current density was reduced by two orders of magnitude,and the detection rate of the devices was more than 10¹² Jones in the wavelength range of 520-890 nm.The voltage and current response of the flexible organic photodetector prepared on the flexible PET substrate is comparable to that of the glass ITO substrate,and the linear dynamic range of the device reaches 101.8 d B.The changes of resting and exercise heart rate can be detected by using the device.（2）The organic upconversion device is prepared,and the biological imaging system is built with the device,and the brightness defect analysis is carried out on the imaging results.Due to the problems of the device preparation process and imaging light source,the negative has black spot defects and uneven brightness.To solve these problems,this thesis proposes a bad spot elimination and brightness uniformity correction method based on negative compensation,which can realize the bad spot compensation of the negative,improve the brightness uniformity to a certain extent,and improve the clarity and cleanliness of the image.In addition,this thesis proposes an adaptive image enhancement method based on negatives,in which the subject of the image is extracted from the background and enhanced separately.Through this method,the details of the specimen are improved,which provides a method for the imaging of fine biological tissues using upconversion in the future.