Research On Photodetector Based On PbSe Quantum Dots/MoS₂

Low-cost,wide-spectrum infrared photoelectric detectors are important components of industrial control,optical communication and biological imaging applications,but most of the current detectors are too expensive to be widely used.Among them,the use of colloidal quantum dots and two-dimensional materials is an attractive alternative to designing low-cost infrared photodetectors.In this thesis,based on the preparation of MoS₂and PbSe quantum dots,combining the characteristics of high carrier mobility of MoS₂,adjustable band gap of PbSe quantum dots and high absorption coefficient,a hybrid photodetector of PbSe quantum dots/MoS₂was constructed and the photoelectric detection performance of the device was analyzed.In this thesis,stable PbSe colloidal quantum dots with different absorption peaks were obtained by controlling the reaction time of synthesis of quantum dots by thermal injection method.As the reaction time increased from 100s to 220s,the size of quantum dots increased from 4.74 nm to 7.11 nm.The position of the first exciton absorption peak also increased from 1580 nm to 2080 nm,and the corresponding optical band gap also decreased from 0.785 e V to 0.596 e V.The characteristic of adjustable near infrared absorption peak provides the possibility to prepare low-cost and wide spectrum infrared photoelectric detectors.In addition,good quality multilayer MoS₂were obtained by mechanical stripping,which extended the spectral detection range due to reduced band gap and resulted in greater absorption due to increased thickness.In this thesis,a PbSe quantum dot/MoS₂ hybrid photodetector was prepared by uv-lithography,electron beam evaporation and spin coating.Multilayer MoS₂as channel material and PbSe quantum dots as photosensitive material were combined to build phototransistor structure,and the embedded electric field was generated in MoS₂channel and quantum dot interface to realize photoelectric detection.PbSe quantum dot/MoS₂hybrid devices show the characteristics of wide spectrum response and successfully broaden the detection cutoff wavelength of MoS₂based photodetectors.The responsivity of P/N PbSe quantum dot/MoS₂photodetector reaches 2300 A/W at650 nm,and the normalized detection rate D*reaches 3.14×10¹⁰Jones.At 1310 nm near infrared,the photoresponsivity is 218 A/W,the D*is 6.84×10~9Jones,the EQE is2.07×10~4%,and the response time is 12.3 ms and 34.2 ms,respectively.The n/n⁺-type PbSe quantum dot/MoS₂photodetector achieves 2787 A/W and 3.85×10¹⁰Jones at650 nm.At 1310 nm near infrared,the responsivity reaches 294.56 A/W,D*is1.32×10¹⁰Jones,and the external quantum efficiency reaches 2.80×10~4%.In particular,the response time of the device reaches?s level in the communication band(1310 nm and 1550 nm),and the rise time and fall time of the device are as low as 83.0?s and90.5?s at 1550 nm incident light,respectively.In addition,after a long time of testing,the hybrid device has good stability in the air.This work provides reference significance and value for the fabrication of low-cost devices in the short-wave infrared band.