Preparation Of PbSe Thin Films By Chemical Bath Deposition And Study Of Their Photoelectric Properties

PbSe is a kind of compound semiconductor material with unique structure,which is characterized by narrow band gap,large exciton Bohr radius,high carrier mobility and large dielectric constant.Due to its excellent optical and photoelectric properties in the infrared range,PbSe is widely used in infrared photodetectors,photoresistors,solar cells and photoelectric emitters.Elements doping has been proved to form unique structures within PbSe,in addition,the band structure can be adjusted to improve its photoelectric performance by controlling the composition and microstructure.In this paper,Ca-doped and Sn-doped PbSe thin films were respectively prepared in one step by chemical bath deposition(CBD).The impacts of dopants concentration and sensitization on the crystal structure,band structure and photoelectric properties of the thin films were investigated.The crystal structure,chemical state and micro-morphology of the films were studied by XRD,XPS,SEM,etc.FTIR was adopted to examin the infrared optical properties,and the optical band gap was calculated.Infrared photoelectric devices based on PbSe thin films were prepared,and the photoelectric detection performance of the devices was tested.The results of the study are shown below.1)The band gap of the films can be adjusted,and the photoelectric performance of the devices were improved by Ca doping.In the range of low dopant concentration 1-5mmol/L,the light responsiveness of the film increases with the increase of Ca dopant concentration.When the dopant concentration is 5 mmol/L,the resistance change rate of the film reaches 16%.Compared with before undoped,it is increased by 4 times.After the doping process,the optical band gap of the film decreases.2)After iodine sensitization,Pb_1.785I_3.570phase was detected in the Ca-doped PbSe films.Compared with before sensitization,the photoelectric performance of the film after sensitization is significantly improved.After sensitization,the carrier recombination becomes faster and the resistance change rate increases.Among them,after the iodine sensitization treatment was performed on the film with a dopant concentration of 3 mmol/L,the resistance change rate of the film reached about 23%,which was more than 4 times higher than before sensitization.3)After Sn doping,some Pb atoms in the PbSe film were substituted by Sn atoms,and a new chemical state of Sn Se appeared.The film is thin,and the thickness is tens of nanometers.Different amounts of ammonia or doping concentration have an effect on the microstructure parameters of the film.When the concentration of Sn dopant is 0.02 mol/L,at the moment of infrared irradiation,the resistance of the film changes the most,there is a significant step down,and the light responsiveness is the best,but there is a problem of poor circulation.The band gap of the film is in the range of0.220-0.264 e V.4)By iodine sensitization treatment,I bonded with Pb in the thin films to form Pb I₂.The photoelectric performance results show that the cycle stability of the thin films is improved by air annealing,the responsitivity,however,depends on the iodine atmosphere in sensitization process.Iodine sensitization treatment is applicable to PbSe thin films with different Sn concentration,and the photoelectric performance could be significantly improved by a suitable iodine concentration.For the thin film with a dopant concentration of 0.02 mol/L,after heat treatment in an iodine atmosphere of 0.005 g/10 g,the resistance change rate increased by about2 times.