Controllable Structures And Photoelectric Properties Of Non - Platinum Substrate Electrode Materials

Dye-sensitized solar cells(DSSCs) have attracted great research interest due to their potential in converting sunlight into electricity and solving the energy problem. Generally, a DSSC is made up of photoanode, dye sensitizers, redox electrolytes and counter electrode. In terms of the material for the counter electrode, it plays a key role that collects the electrons from the circuit and catalyze the reduction of I3-. In order to reduce I3- to I- with a minimum energy loss on the CE, efficient electro-catalysts are required. In this thesis, a series of composite counter electrodes(carbon material/metal carbide, transition-metal sulfide) were fabricated, they hold the merits of low cost, high stability and high efficiency. And the relationship between the experimental parameters(e.g. ratio of the raw material, interaction among the component) and the energy conversion efficiency, catalytic activity of the DSSCs was investigated. The main contents of this paper are as follows:1) highly crystalline graphitic carbon(GC)/Fe3 C nanocomposites have been prepared by a facile solid-state pyrolysis approach and used as counter electrode materials for high-efficiency dye-sensitized solar cells. The content of Fe3 C in the composites can be modi?ed by different hydrochloric acid treatment time. In comparison with pure highly crystalline GC, the DSSC based on GC/Fe3 C nanocomposite with 13.5 wt % Fe3 C content shows higher conversion efficiency(6.04%), which indicates a comparable performance to the Pt-based DSSC(6.4%) as well, resulting from the perfect electron transfer of GC and electrocatalytic activity of Fe3 C.2) Fe3W3C/WC/graphitic carbon(GC) ternary nanojunction hybrids are synthesized through a solid-state pyrolysis process for dye-sensitized solar cells. First-principles calculations have been first employed to investigate the adsorption energy between I3- and Fe3W3 C and WC nanoclusters. Scanning Kelvin probe images indicate that the work function changes greatly due to the formation of ternary nanojunctions, which favor fast photoelectron transfer. A photoelectrical conversion efficiency of 7.1% is achieved based on Fe3W3 C /WC/GC hybrid counter electrodes, which is much higher than those of pure GC(5.02%) and WC/GC hybrids(6.11%), which can be attributed to fast photoelectron transfer due to the ternary junctions and the addition of Fe3W3 C with more catalytic metallic atoms.3) a facile one-step hydrothermal method was used to prepare a Ni S/Ni3S2 nanorod composite that directly grows on the Ni foil, then the material was directly used as counter electrode of DSSCs. High photoelectrical conversion efficiency based on Ni S/Ni3S2(7.20%) has been obtained, which is comparable to that of DSSC based on Pt(7.56%), that’s because Ni S/Ni3S2 nanorod composite arrays can provide many catalytic active sites and easier electrons transfer.