Surface And Interface Modulation On The Optoelectronic Properties Of Si/ZnO Core/shell Nanowires

Recently,the semiconductor core-shell nanowire(CSN~W)solar cells have wide application prospects in the field of next-generation energy due to the advantages of low cost and high efficiency.In order to further reduce the cost and improve the conversion efficiency,the theoretical prediction of band alignment and relative optoelectronic properties of semiconductor CSNW solar cells is a grand challenge.Accurate calculation of corresponding band offsets of the core and shell parts can not only enhance the understanding about the underlying mechanism of the electronic properties,but also help to guide the further optimization of system performances.As the size of the CSNWs decreases,the surface dangling bonds,high surface-to-volume ratio(SVR)and coordination defects can lead to a new self-equilibrium state,which changes the optical and electronic properties of the system.But the power conversion efficiency(PCE)is still low due to the high carrier recombination in nanostructures.Therefore,how to suppress the electron and hole recombination has become an urgent scientific problem in the field of quantum energy.In this paper,based on atomic-bond-relaxation(ABR)correlation mechanism and detailed balance principle(DBP),we not only study the size-dependent theoretical relationship of band offset and band alignment,but also predict the optoelectronic conversion properties of the nanosystem.Also,we establish the theoretical model of size-dependent PCE.First,we systematically study the band offset of Si/ZnO CSNWs with different diameters and epitaxial layer thicknesses.Second,we calculate the band alignment of Si/ZnO core/shell heterojunctions under different sizes.Third,we establish the theoretical relationship between the PCE of Si/ZnO CSNW solar cells and the size.The mainly achievements are shown as follows:(1)According to the ABR correlation mechanism,we study the size-dependent bandgap and band offset of Si/ZnO CSNWs.It is found that the bandgap of core is evidently blue shift with reducing diameter and ZnO epitaxial layer,the offset of the band will increase with the decrease of size.We also reveal that the band engineering by the lattice strain that can induce the type-?/? transition.(2)Combined with the DBP and ABR,we establish the size-and thickness-dependent recombination rate and the theoretical relationship between the PCE and the size of Si/ZnO CSNW solar cells.It is found that the PCE of Si/ZnO CSNW solar cells increases with increasing diameter of Si when the diameter of SiNWs is less than 105 nm.In addition,as the thickness of epitaxial layer increases,the PCE also increases.