Preparation Of Organic Light Detectors And Their Application In Smart Sites

In recent years,as China’s national economy continues to develop at a rapid pace,the urbanization process continues to advance,and the scale of the construction industry is also growing year by year.With the concept of smart earth and smart city,smart construction site and other related intellectual products have been rapidly developed.The Internet of Things(Io T)technology is one of the important technologies for smart cities,linking things together on construction sites through countless sensors.Optical sensors are a very important type of sensors,and different types of sensors are usually required for different application scenarios.As an interdisciplinary project between electronics and civil engineering,the main research work in this paper revolves around the preparation of two types of detectors with different detection wavelengths: visible light detectors and near-infrared detectors.The visible light detectors are used when there is sufficient light.Thin films of gold nanoparticles(Au NPs)with different thicknesses were prepared,and it was confirmed that the average particle diameter of Au NPs becomes progressively larger and the absorption spectrum is redshifted as the film thickness increases.The Au NPs were then introduced into a PTCDI-C8-based organic photosensitive transistor(OPT),and the OPT with a 3 nm thick Au NPs film was found to have the best performance.Under red light irradiation,the photosensitivity P,photoresponse rate R,specific detection rate D* and external quantum efficiency EQE of the OPT can reach 6.21 ×105,24.12 A/W,2.85 × 1011 Jones and 453.58 %,respectively,which meet or even exceed the highest values reported so far for red light detectors.In addition,the performance of the OPT is significantly improved under green light irradiation at 532 nm.The physical mechanism responsible for the excellent performance of the device is analyzed,and it is suggested that the effects of near-field enhancement,far-field scattering,interband charge transfer,and high photoconductor gain caused by the introduction of Au NPs lead to an increase in the EQE of the outer quantum efficiency of the OPT,which in turn improves the detection efficiency of the light detector,resulting in a high-performance visible-light detector.When there is insufficient light,an infrared detector is used.Due to the scarcity of organic semiconductor materials in the infrared band,the application of organic photodetectors in the near-infrared band is greatly limited.The charge transfer complex(CTC)is co-evaporated with the metal oxide WO3 and the organic semiconductor m-MTDATA,which has excellent absorption properties in the infrared band 1000-1400 nm.Using CTC as the photosensitive layer and pentacene as the active layer,a high-performance NIR OPT with an optical responsivity R exceeding that of recently reported 1.1 um band inorganic IR detectors was prepared.In addition,the working mechanism of the organic phototransistor based on pentaphenyl-CTC is described by energy band analysis,and the thickness of CTC layer is optimized.The application scenarios of organic photodetectors in smart construction sites are studied.For example,image sensing function to realize fire alarm system by light detector,intelligent adjustment of screen and light brightness to achieve energy saving by ambient light detection system,laser distance measurement by NIR light detector +NIR laser,crane lifting safety by infrared proximity sensor and biometric scanning by NIR detector.Therefore,the potential application of organic light detectors in intelligent construction sites is very broad.