| As one novel solar cell, dye-sensitized solar cells (DSCs) have attracted considerable attentions due to their merits including high efficiency in theoretical, easy of process in production, abundant in raw materials and competent under weak light. Of the three components in DSCs, the counter electrode (CE) is responsible for collecting electrons from external circuit and then catalyzing the reduction of oxide constituent within the electrolyte. Noble metal Pt is the earliest and most widely used CE material, however, the high price, the very limited reserve and the difficulty in recovering will increase the production cost of DSCs Besides, for industrialization it is needed to prepare large scale Pt CEs whereas corresponding method is absent. Therefore, reducing the amount of Pt or exploiting simple and controllable method to prepare large-scale Pt CEs is of great significance. The thesis is composed of two parts. Firstly, we developed a new method to produce large-scale Pt CE, by which the amount of Pt was decreased while corresponding DSCs still achieved high performance. Secondly, we firstly applied the single-atom Pt composite material into CEs of DSCs, then following with systematic investigations of the electrocatalytic behaviors and high efficiency in DSCs.Part I:We explored one method for preparing Pt CEs with screen printing technique. Paste was prepared and optimized in composition, Pt CEs were then prepared by screen-printing. Firstly, the effect of surfactants on the mechanical adhesion and dispersity of Pt nanoparticles were investigated, results indicated that adding surfactant into paste was beneficial to the dispersity and mechanical adhesion between Pt nanoparticle and FTO substrate. Secondly, the effect of sintering temperature on the catalytic activity of Pt CEs was studied. Results showed that Pt CEs prepared at400℃had a higher catalytic activity. Thirdly, Pt CEs prepared through screen-printing were compared with those prepared by spin-coating and two-step dip-coating methods. Results showed that the series resistance (Rs) and charge transfer resistance (Rct) of the screen-printed Pt CE were lower than that of other CEs, in addition, corresponding DSC had a higher photoelectric conversion efficiency (PCE).Part II:For the system of composite CE based on Pt single atoms, we firstly confirmed the existence state of Pt on FeOx which served as the substate. Results indicated that, when the loading amount of Pt was0.08%(vs. FeOx), Pt attached on FeOx in the form of single atoms. With the increase of Pt loading, it was changed from single atoms to clusters, sub-nanopartilces and even nanoparticles. Used as the CE for DSCs, it was found that the PCE of the DSC based on the0.08%Pt/FeOx CE was twice that of the one based on bare FeOx, illustrating the best utilization of Pt. With more and more Pt on FeOx, the PCE of DSCs increased gradually, however, the catalytic efficiency of per weight unit of Pt and the atomic utilization of Pt decreased. The electrochemical characterizations of these Pt/FeOx CEs were performed and the results showed that Rct decreased and catalytic activity increased gradually with more and more Pt on FeOx. Finally, it was thought that the poor conductivity and nanoporous structure of FeOx restricted the further increase of photovoltaic performance of DSCs. |
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