Study On Wide Spectrum Photodetector Based On Lead Selenide Quantum Dots

Traditional infrared photodetectors,such as In Ga As,are difficult to be applied in various fields due to their complex preparation process and high preparation cost.Colloidal Quantum dots(CQDs),as a potential low-dimensional semiconductor nanomaterial,has being increasingly used in the fields of photoelectric detectors,light-emitting diodes and solar cells due to its advantages of simple preparation process,adjustable band gap and low cost.Among them,the photodetectors prepared by lead selenide colloidal quantum dots(PbSe CQDs)can not only meet the detection requirements of visible-short-wave infrared,but also have high responsivity in each band.This thesis studies the preparation of PbSe CQDs by thermal injection,and combined with photoconductor and photodiode to prepare quantum dot photodetector capable of wide-spectrum detection(400-2600 nm).In this thesis,the preparation technology of PbSe CQDs synthesized by thermal injection method was firstly studied,and CQDs with different particle size were obtained by adjusting the growth temperature and time during the synthesis process.The sizes of these CQDs ranged from4.0 nm to 24.0 nm.Subsequently,the particle size distribution of CQDs under different synthesis conditions was analyzed,and it was found that the monodispersion of the CQDs synthesized by adjusting the growth time was poor.By contrast,the monodispersion of the CQDs synthesized by adjusting the growth temperature was better,which could better meet the requirements of photodetectors.Then,the absorption spectra of the synthesized CQDs at different growth temperatures were characterized.It was found that the absorption peak of the synthesized CQDs could be adjusted from 1900 nm to 2500 nm,and the synthesized quantum dots with a size of about 10 nm have a spectral absorption range of 400-2600 nm.Secondly,based on the synthesized PbSe CQDs,PbSe quantum dot films were prepared by spin-coating method.The preparation of quantum dot films is studied from the selection of solvent,concentration of solution,number of spin-coating and baking temperature of the film.The preparation of quantum dot films with low surface roughness and thickness of controllable were completed through the study of the process parameters,which laid a foundation for the subsequent preparation of photodiode detector.Finally,after the synthesis of PbSe CQDs and the study of thin films,this thesis uses spinning coating,thermal evaporation and other processes to prepare a wide spectrum photodetector based on PbSe CQDs.Firstly,a typical PbSe quantum dot photoconductor is prepared by selecting CQDs with a size of about 10 nm.By applying an external bias voltage,the photodetector can detect a wide spectrum in the range of 400-2600 nm.The responsivity of the detector in the infrared band is up to 320 m A/W.External quantum efficiency is over 14%.However,due to the shortcomings of external bias voltage,slow response speed and low specific detection rate,this thesis then prepared the photodiode structure and studied the thickness of Zn O to optimize the performance of the device.The device has a maximum specific detection rate of1.5×10¹⁰ Jones in the short-wave infrared range and a response time of 0.3 ms.