Research On Heterojunction Photodetectors Based On Infrared Colloidal Quantum Dots

Based on traditional semiconductor materials(such as Si,Ge,In Ga Sn,etc.)photodetectors are often used to fabricate planar chips with small area.The emergence of colloidal quantum dots prepared by non-traditional methods such as liquid phase synthesis makes it possible to fabricate electronical devices with high performances or flexible characteristics.By constructing heterojunctions,two or more materials with different Femi energy can be integrated into a composite system.In order to develop a photoelectric detector based on infrared colloidal quantum dots for wide spectrum detection,ultra-fast response and high detection sensitivity,the heterojunction is constructed by using infrared colloidal quantum dots(including PbS,PbSe and Cu In Se₂ quantum dots)combined with Perovskite thin film,new two-dimensional materials and new Perovskite quantum dot.The way of heterojunction is investigated from three aspects:material,device structure and photosensitive physical mechanism.The main work of this dissertation can be divided into the following aspects.1.In order to improve characteristics including detection wavelength range,response time,and responsivity,broadband field effect phototransistors based on CH₃NH₃Pb I₃ perovskite-PbSe colloidal quantum dots heterostructures are manufactured in a cost-effective,solution-processed strategy.The phototransistor exhibits bipolar behaviors and a wide spectral response ranging from 300 nm to 1500nm.A field effect phototransistor has been fabricated by single layer WS₂ with decoration of PbS quantum dots through a low-cost,solution-processed strategy.The phototransistor exhibits a rapid response of?200?s with the assistance of the WS₂/PbS heterojunction.Furthermore,based on the strong light absorption characteristics of quantum confinement effect,field effect phototransistors based on Cs Pb Br₃/PbS colloidal quantum dots heterostructures are fabricated through a low-cost,solution-processed strategy.The responsivity of the device is as high as 4.5×10⁵A/W,which is three orders of magnitude higher than that of the device constructed by single material system.2.Furthermore,in order to improve performances of the device,plasmonic lead-free Cu In Se₂ quantum dots field effect phototransistors are fabricated through a low-cost,solution-processed strategy.The field effect phototransistor exhibits self-powered multi-wavelength response,particularly,for 405nm,532nm and 808nm irradiations.It is worth mentioning that the relevant properties including small dark current and high responsivity can be enhanced after considering Au nanoparticles located surface plasmonic response(LSFR)effect.In addition,broadband phototransistors based on Cs Pb Br₃/PbS colloidal quantum dots heterostructures were fabricated through a low-cost,solution-processed strategy.The phototransistor exhibits better performance than traditional parallel channel devices.3.Aiming at the application of photodetectors in array imaging,heterojunction phototransistor arrays for multi-band optical sensing and real-time imaging have been investigated.Cs Pb Br₃ perovskite colloidal quantum dots and PbS colloidal quantum dots synthesized by a more efficient and low-cost solution method are used to construct heterojunctions.As the photosensitive layer of the detector,the detector arrays with 10×10=100 structural units are fabricated,and the real-time imaging test system is built by using the relay array controlled by programmable logic controller(PLC).