Study On Silicon-based Ge Quantum Dots And Silicon Nanowires And Their Applications In Photovoltaic Cells

Germanium quantum dots and silicon nanowires are semiconductor nanomaterials with excellent photoelectric properties.Ge QDs have unique near-infrared absorption properties,and SiNWs have good antireflection characteristics.They can be used in photovoltaic cells to greatly widen the range of absorption spectrum and reduce the reflection of light.Therefore,the conversion efficiency of PV cells can be improved.In this thesis,the growth of C-induced high-density Ge/Si QDs is realized by magnetron sputtering.The process of preparing SiNWs on n-type silicon substrates is studied by MACE method.The Ohmic contact Ag electrode was fabricated by magnetron sputtering,and the silicon-organic hybrid photovoltaic cells was assembled.The main tasks are as follows:1.High density Ge QDs are grown by DC magnetron sputtering,and the density,size and crystallinity of Ge QDs were studied by adjusting the growth temperature and deposition thickness of Ge layer.In the experiment,It can increase the number of Ge QDs nucleation centers and reduce the thickness of SiGe infiltrating layer by depositing the C induced layer.The experimental results indicate that the density and crystallinity of Ge QDs increased firstly and then decreased with the increase of growth temperature,and the optimal results is achieved at 650?,the density of Ge QDs is 1.01x10¹¹ cm^-2,Its crystallinity is 83.7%.When the deposition thickness of Ge film is 1.5-2.5 nm,the density of Ge QDs increased with the increase of Ge film thickness in the same preparation condition.2.The MACE method is used to etch SiNWs on Si substrates.The results indicate that the concentration of Ag deposition solution?C₁=HF:AgNO₃?and deposition time?t₁?can affect the morphology of SiNWs,when C₁=4.5:0.01 mol/L,t₁=90 s,HF:H₂O₂=4:1mL,the morphology of SiNWs is the best,the size is uniform,and the etching rate of SiNWs is about 1.38?m/min.The reflectivity of SiNWs decreased with the increase of the length.3.Ag films are sputtered on the silicon substrates by magnetron sputtering,and the sample is annealed at different temperatures,finally the Ohmic contact Ag electrode was obtained.The experimental results indicate that the compactness of Ag films can be improved by adjusting the sputtering power and pressure.It can reduce the defect density and the number of grain boundaries,improve the crystallinity and reduce the contact barrier by annealing.Then,the Solar photovoltaic cells combining silicon-based nanometer materials?Ge QDs?SiNWs?with PEDOT:PSS were assembled,and the I-V characteristic curve was tested.The short circuit current density and power conversion efficiency of PV cells were obviously improved,and the efficiency of SiNWs type PV cells reached 7.10%.