Applications Of Graphene And Graphene Quantum Dots In Silicon Based Solar Cells

As a two-dimensional layered materials,graphene possess high carrier mobility and high conductivity,high light transmission as well as stable physical and chemical properties,since discovered in 2004,graphene has obtained attention around the world and has wide range of applications in various fields,especially in optoelectronics research field,such as transparent electrodes,super capacitors,ultrafast devices,but its zero band gap characteristics restrict the further application.Graphene quantum dots(GQDs),as a graphene derivative,its band gap is tunable and has remarkable quantum confinement and edge effect,which endow its unique photoelectric transmission characteristics,can effectively supplement the boundedness of graphene.This paper mainly discusses some applications of graphene and graphene quantum dots in silicon-based heterojunction solar cells.The main contents and conclusions are as follows:1.We use graphene synthesized with CVD method as transparent electrodes in the crystal Si/PEDOT:PSS organic-inorganic hybrid solar cells,the device exhibits excellent photovoltaic performance.Compared to the commonly used silver grid electrodes,graphene electrode has more excellent carrier collection capacities.In order to further enhance the light absorption of the device,we constructed a new model based on "PMMA-PEDOT:PSS" double antireflection structure.By optimizing the thickness of PEDOT:PSS and PMMA and graphene layers,combined with experimental and theoretical simulations,we finally obtained photovoltaic devices with power conversion efficiency up to 13.01%.In addition,the device shows excellent stability,mainly profit from the high physical and chemical stability of graphene as well as protection for organic layer by graphene elelctrodes,the device can still maintain a good performance in the long-term storage.2.We prepared silicon nanowire(SiNW)arrays utilizing metal-assisted chemical etching(MACE)method,the SiNWs have excellent light-harvesting capacity compared to planar silicon.In this experiment,we use hydrothermal cutting method and prepared GQDs with uniform particle size and tunable bandgap,and constructing GQDs/SiNWs core-shell heterojunction solar cell via a simple drop casting method,and the high transmittance high conductivity graphene is used as transparent electrodes.GQDs can act as electron blocking layer and hole transport layer,which can effectively suppress the recombination of electrons at the anode.By the lifetime characterization,we further verify that GQDs can significantly enhance the minority lifetime of the SiNWs,which mainly due to the strong built-in potential between GQDs and Si.Finally,by optimizing GQDs film layers combining nitric acid doped graphene,we obtained a 12.01%high efficiency heterojunction photovoltaic device.Social problems caused by energy crisis and environmental pollution has attracted humen's attention,the development of clean energy,especially the photovoltaic is particularly important,our research results reveal that graphene and graphene quantum dots have great potential and research value in the field of energy,and also open up a new direction for the future high-efficiency and low-coat silicon-based solar cells.