The Research Of Counter Electrode Based On Graphene And C₆₀ In Dye-sensitized Solar Cells

With the development of economy and a surge in the population of the world, human demand for energy is more and more. At present, human mainly depend on non-renewable fossil fuels, such as oil, natural gas, coal and so on. Studies have demonstrated that fossil energy will be exhausting. Meanwhile the burning of fossil fuels produces large amounts of greenhouse gas (carbon dioxide), leading to global warming and acid rain generated from the emission of sulfur dioxide, nitrogen oxide and destroying the natural environment heavily. In order to realize the sustainable development of human, it is urgent to research sustainable clean energy. Solar energy is green and abundant, can be used all over the world and also can be explored locally. It attracts more and more attention from all over the world. Dye sensitized solar cells (DSSCs), as a way of solar photovoltaic utilization, are low cost, green. They can be fabricated easily and have high conversion efficiency. They have already attracted more and more scientific researchers and they can be used widely in human’s life. Dye sensitized cells can be devided into n-and p-type Dye sensitized solar cells (n-DSSC, p-DSSC). DSSCs consist of photoanode (photocathode), electrolyte and the courter electrode (CE), in which the CE plays an important role thorugh collecting and transfering carrier, adsorbing and catalyzing electrolyte as well as reflecting light. At present, little research focus on counter electrode of p-DSSC. In addition, Pt deposited on FTO is expensive and isn’t suitable for commercialization. In this paper, low cost and high efficient CEs of DSSC are evaluated to replace precious Pt.The first chapter introduces the classification, structure and principle of DSSCs, the research progress of photoanode (photocathode) material, dye, CE and some problems and trend of development of DSSCs.The second chapter mainly introduces the characterization methods of DSSCs and measuring methods. DSSCs basic characterization methods are:SEM morphology characterization, XRD component identification, infrared functional group analysis, UV-Vis, cyclic voltammetry analysis catalytic properties, ac impedance analysis the interface of DSSCs and photoelectric performance parameters (I-V, FF, PCE and IPCE) and Ultra High Vacuum Multi-function Sample Preparation system.The third chapter is about the preparation and the measurement of DSSCs. This chapter introduces the DSSCs preparation of required materials, measuring instruments, photoanode (photocathode), method of preparation of electrolyte and the electrode.The fourth chapter discuss about using Pt modified thermal evaporated C60 as counter electrode in dye-sensitized solar cell. Through thermal decomposing H2PtCl6 to achieve trace platinum before depositing C60 film by physical vapor deposition method, a composite CE composed of trace Pt and a thin layer of C60 can be prepared. This composite CE can be used in n-DSSCs, achieving a comparable performance to the device with a thick Pt CE. The good performance of Pt/C60 composite CE is ascribed to the fast electron transfer of Pt and the large surface area provided by C60. Thus trace Pt underneath poor conductive materials can be used as an effective way to improve their conductivity. Our studies also demonstrate that trace Pt underneath C60 can be used as a cost effective material to replace precious Pt as CE to get high power conversion efficiency DSSCs.Chapter fifth graphene nanosheet as counter electrode in p-type dye-sensitized solar. Reduced graphene (rGO) was synthesised by Hummers method and dry in vacuum. RGO was dispersed in terpineol containing 5% ethylcellulose, doctor-blade on the FTO, sintering on 400℃ for 15 min. RGO film on FTO observed by SEM is 16 nm thickness and shown 3D network. Further test by CV and EIS performed shown high catalytic activity. GN as CE in p-type DSSCs is explored by comparing with Pt CE, using the system with PI as dye and NiO as photocathode. An open voltage (Voc), a short current (Isc), a fill factor (FF), and a PCE of 134 mV,1.90 mA·cm-2,36.37%, and 0.09% are achieved respectively for a device with GN CE. The performance is comparable with a device using Pt CE (Voc, Isc, FF, and PCE are 140 mV,2.25 mA-cm"2, 31.29%, and 0.10%, respectively). GN films have been demonstrated for the first time to be used as CE in p-type DSSCs.