Photoelectric Properties Of Two-Dimensional GeSe And Its Heterojunction Design

The group-?monochalcogenides?GeSe,SnSe,GeS,SnS?has very excellent photoelectron properties and has received extensive attention in research.Among the single layer structures of these four compounds,only the GeSe single layer is a semiconductor having a direct band gap and has excellent optical properties.Recently,several atomic layers and single-layer GeSe have been successfully prepared by mechanical stripping and laser thinning techniques.Based on this,the photoelectric performance research and device design of two-dimensional GeSe become the key to future application,and it is the current research hotspot.Based on the first-principles calculation method of density functional theory,the electronic and optical properties of single-layer GeSe are first studied.The hybrid functional calculation shows that the single-layer GeSe has a direct band gap of 1.71eV,the carrier mobility reaches 10³ orders of magnitude,and the optical absorption coefficient can reach 10⁵ cm-1,which has excellent application prospects for semiconductor devices.Through different ways of stacking structure design,it is found that AA and AC stacks have indirect band gaps,while AB and AD stacks have direct band gaps.Studies have also shown that the two-atomic layer GeSe of AB stacks is applied in the zigzag direction.Uniaxial strain can adjust the width of the direct band gap over a wide range.Based on the study of single-layer GeSe and two-layer stacking,the photovoltaic application of single-layer GeSe was explored by constructing a heterojunction.A heterojunction composed of a single layer of GeSe and graphene was designed and found to form a Schottky contact.In the formed GeSe/graphene heterojunction,the energy band calculation found that the direct band gap of the single layer GeSe and the Dirac cone of the graphene can be maintained.By adjusting the interlayer spacing,it was found that the Schottky barrier height of the GeSe/graphene heterojunction can be adjusted,and the graphene opens a band gap of 0.17 eV.It is found that both the applied electric field and the strain can adjust the Schottky barrier height and contact type of the GeSe/graphene heterojunction,which can be used as a Schottky device.A heterojunction composed of a single layer of GeSe and a single layer of the same cluster compound is considered,and a heterojunction composed of a single layer of GeSe and a single layer of SnSe is designed by calculation.It is found that the GeSe/SnSe two-dimensional heterojunction has a type II energy band with a band size of 0.89 eV and a high optical absorption coefficient.Theoretical calculations show that the photoelectric conversion efficiency of GeSe/SnSe two-dimensional heterojunction can reach 21.47%,which is higher than the two-dimensional heterojunction composed of molybdenum disulfide and black phosphorus.The calculations show that the carrier mobility of the designed GeSe/SnSe two-dimensional heterojunction can reach 10⁴ cm²V^-1s^-1.The GeSe/SnSe two-dimensional heterojunction with the type II energy band,high photoelectric conversion efficiency and high carrier mobility has application prospects in solar cell applications.