Engineering Eco-friendly Mn/sn-doped CuInSe/ZnSe Core/Shell Quantum Dots For Photodetector Application

Quantum dots are nanocrystals with easy synthesis and tunable composition and structure.Among them,CuInSe₂ colloidal quantum dots are a kind of semiconductor nanomaterials that can change the band gap as needed.Because they do not contain toxic elements such as lead,mercury,and cadmium,CuInSe₂ colloidal quantum dots are more friendly to the human living environment.Due to the large number of trap states on the surface,the photogenerated carriers generated by CuInSe₂ colloidal quantum dots will undergo serious non-radiative recombination,which will directly affect the performance of CuInSe₂quantum dot photodetectors.In view of the above problems,CuInSe₂colloidal quantum dots are doped with manganese ions and tin ions in this paper.By doping with manganese ions,the transfer efficiency of photogenerated carriers generated by quantum dots in the device is increased.The doping of quantum dots realizes the near-infrared regulation of quantum dots.On the basis of doping,a ZnSe shell structure is grown on the surface of the corresponding core quantum dot,which greatly reduces the density of trap states on the surface of the quantum dot,and realizes the high efficiency of the colloidal quantum dot photodetector in the visible light and near-infrared bands photodetection.The specific contents of this research are as follows:(1)In order to improve the crystallinity of quantum dots and reduce the density of trap states on the surface of quantum dots,MnCuInSe colloidal quantum dots were obtained by introducing manganese ions.On this basis,ZnSe shell structures with different thicknesses were grown on the surface of MnCuInSe core quantum dots,and MnCuInSe/0.5ZnSe,MnCuInSe/1.0ZnSe and MnCuInSe/1.5ZnSe were obtained,respectively.With the continuous thickening of the ZnSe shell,its absorption and fluorescence continued to blue-shift.By testing the performance of the photodetectors assembled with the above three core-shell quantum dots,it was found that the optimal sample was MnCuInSe/1.0ZnSe,with a responsivity of 3.417 A/W and a detection rate of 3.8x10¹⁰ Jones at 450 nm.The responsivity in the 520 nm band reaches 1.985 A/W,and the detection rate reaches 4.14x10¹⁰ Jones.(2)In order to further adjust the absorption range of CuInSe₂ to the near-infrared band,CuInSnSe nuclear quantum dots were obtained by introducing tin ions in this work.Since CuInSnSe core quantum dots are extremely unstable,a ZnSe shell structure is grown on the surface of CuInSnSe core quantum dots to obtain CuInSnSe/ZnSe core-shell quantum dots.The band gap was successfully adjusted from 1.6 e V to 1.9 e V.The effective surface passivation of CuInSnSe quantum dots through the ZnSe shell layer improves the optical properties of quantum dots.(3)The above-mentioned CuInSnSe/ZnSe core-shell quantum dots were sensitized on the mesoporous titania film by electrophoretic deposition,and the CuInSnSe/ZnSe quantum dot photodetector was assembled.The responsivity of the photodetector in the790 nm band is 0.95 A/W,and the detection rate is 1.74×10¹⁰Jones.The responsivity reaches 0.16 A/W in the 980 nm band,and the detection rate reaches 2.75x10~9Jones.The above data show that the CuInSnSe/ZnSe quantum dot photodetector fabricated in this work truly realizes near-infrared photodetection.