Electrolyte Additives And Counter Electrodes Of Dye-Sensitized Solar Cells

DSSCs consist of 3 components, which are photoanodes, electrolytes and counter electrodes. In the traditional liquid electrolytes, additives are added into them to get good performance of DSSCs. The effect of additives is limitted, which may only obviously improve Voc or Jsc. Pt is widely accepted as the traditional counter electrode because of the good conductivity and the catalytic properties. So various non-Pt counter electrodes such as carbon materials, conductive polymer materials, metal sulfide materials and metal oxide materials have attracted wide attention and application. On the other hand, the performance of counter electrode materials can be also tuned through modifying the surface atomic geometrical and electronic structures, which can create more active sites for the heterogeneous electrocatalysis process of redox mediators. In order to improve the performance of DSSCs based on the electrolyte additives and counter electrodes, the major elements are as follows:1) Different proportions TBP and GuSCN liquid electrolyte are prepared. We use the electrochemical and Photoelectrochemical tests and theoretical calculation to study the mechanism of affecting the performance of DSSCs. The co-additives of TBP and GuSCN in electrolytes can prominently affect the photovoltaic behavior of DSSCs due to their advantages fitting with energy levels and charge transfer. MS analysis is used to quantify the TiO2 band edge movement to clarify the change of Voc. The corresponding kinetic investigations are carried out using CV, EIS, MPS/IMVS and CE. Theoretically, DFT theory method is performed to explore the interacting energy, Fermi energy and frontier orbitals properties. The results show that the performance of DSSCs is best when the proportion of TBP and GuSCN is 9:1. the frontier orbitals between TBP and TiO2 are sufficiently overlapped to induce the negative shift of Fermi energy, increasing Voc. G+ can be tightly absorbed on TiO2 surface to form a passivated layer due to the Coulomb attraction, depressing the recombination rate. The different proportion of TBP and GuSCN would produce a competitive effect, which would becaused by their volume and electrostatic effect. The photovoltaic performance might be as a result of a synergistic effect of co-additives.2) A new kind of counter electrodes based on FTO material was designed. FTO is annealed in the tube furnace in vacuum, and then applied as counter electrodes of DSSCs. The result show that the highest efficiency can achieve 90% of Pt. So as to explain the reason of the catalytic property, SnO2 film is prepared using PLD deposition method, and then annealed in the same atmosphere with FTO. Applied as counter electrodes of DSSCs, the efficiency can achieve the same level of Pt. At the same time, IV, CV, and Tafel tests are used to examine the good catalytic properties of these counter electrode materials. On the other hand, ESR is also applied to prove that the reason is the oxygen vacancies.