Preparation Of The Ruthenium-based Alloy Counter Electrodes And Research On The Photovoltaic Performance For The Dye-sensitized Solar Cells

As an important component of the dye-sensitied solar cells (DSSCs), the counter electrode (CE) plays a crucial role both in the electrocatalysis for I-/I3- redox reaction in the electrolyte and participation in collecting and transmitting for external electronic. Hence, the photovoltaic properties of the global cell have been significantly determined by the electrical conductivity, electric catalytic activity and the stability of the CE materials. The Platinum plated conducting substrates are conventional used as standard CE of DSSC, because of its high electrical conductivity, catalytic activity and good chemical stability. However, Platinum is precious metal and limited in the natural reserves, which hinder the industrial mass production of DSSC. It plays a profound scientific significance that seeking advanced materials with superior performance as Pt alternatives and reducing the cost of CEs. In this thesis, we systematically investigated the production of a range of CEs including GO/PANi composite, Pt-Ru alloy, Ru-Se alloy and the effect of them on the performance of DSSC.Layer-by-layer (LBL) self-assembly provides a facile method to architecture well-defined nano-structures with excellent electrical, electrochemical properties. Here, the electrical and electrochemical behavior of the LBL self-assembly PANi-(GO/PANi)n conductive multi-films are studied. The research results indicate that the conductive multi-films grow linearly and uniformly, and the thickness of each GO/PANi bilayer is basically the same. The redox reaction kinetics in the Sulfuric acid electrolyte are controlled by the diffusion process. The electrical conductivity of the conductive multi-films presents linear relationship with the bilayer numbers, which indicating linear increments in surface charge accumulation with increasing bilayer number, illustrating the electron tunneling effect. The catalytic activity toward I-/I3- redox couple of the conductive multi-films is enhanced with increasing bilayer number, and the charge transfer dynamics for I-/I3- redox reaction are controlled by membrane charge diffusion process. The DSSC employing PANi-(GO/PANi)4 CE gives a promising power conversion efficiency of 7.41%, in comparison with 6.37% from PANi-(GO/PANi)1 CE. Self-assembly technology provides new approach for fabricating efficient DSSC, and new efficiency record is expected to be surpassed.Carbon and conductive polymer materials have advantages in aspects like sources or preparation technologys, and some achievements of these kinds CEs-based DSSC have been obtained, nonetheless, its conductive ability remains to be improved when compared with the metallic materials. In view of the outstanding results of alloy catalysts achieved in fuel cell field, Pt-Ru alloy CEs are synthesized using a low-temperature hydrothermal technique, which are applied to DSSCs for photovoltaic testing. SEM observations give homogeneously nanofibers for PtRu3 alloy CE, which afford large active area for I-/I3- redox couple that can facilitate the catalytic activity. The electro-catalytic properties of the Pt-Ru alloy CE are characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafer polarization curve, giving results that PtRu3 alloy CE catalyzes more effective and more stable in I-/I3- electrolyte than Pt CE. A power conversion efficiency of 6.80% is obtained for DSSC equipped with PtRu3 alloy CE, compared with 6.17% from Pt-based DSSC.Energy conversion efficiency of DSSC can be facilitated by the way of enhancing the light capture rate. Transition metal selenides possess unique electronic structure, and Ru-Se alloy CEs are synthesized by low-temperature hydrothermal approach. SEM observations indicate the Ruo 33Se alloy CE with homogeneous mesoporous structures, which can provide abundant transmission channels for I-/I3- redox couple and tremendous effective surface for redox reactions. Electrochemical testing results demonstrate higher electro-catalytic activity towords I-/I3- of Ru-Se alloy CE compared with Pt CE. Optical transmission spectra reveals that Ru-Se alloy CEs display high optical transparency. Employing these transparency Ru-Se alloy CEs into bifacial DSSCs, the photovoltaic performances are discussed when irradiation from the front, rear and both sides, respectively, displaying optimal front and rear efficiencies of 8.76% and 5.90%, respectively. When the DSSC device is irradiated from both sides, the maximum power output has also been markedly enhanced in comparison with Pt-based DSSC. The results suggest that, the loss of light from the TiO2 photoanode can be compensated by the incident light from the CE, leading to a markedly increased light harvesting efficiency and enhanced dye excitation. Fast start-up, high multiple start capability, low electron recombination, and good stability are observed from photoelectric stable performance testing, motivating the potential application of such bifacial solar cell systems in engines, vehicles, and power sources.