Photoanode Structure Optimization And Study Of Photoelectric Performance For Dye-Sensitized Solar Cells

Dye-sensitized Solar Cells(DSSCs) belongs to the third generation solar cells. It has a great application prospect due to its simple fabrication process and low cost. It is very suitable for mass production. Currently, the highest power conversion efficiency(PCE) of DSSCs is 12.3%. Compare to the theoretical conversion efficiency of 66%, there is a lot space to improve. So the DSSCs is a good choice to replace the 90% of the current solar market of the silicon cells. It has attracted much attention and research from scientists. In DSSCs, the main factor influencing the PCE is incident photo-to-current efficiency(IPCE). And IPCE is mainly composed of three parts, which are light capture efficiency, charge collection efficiency and electron injection efficiency. The light capture efficiency is mainly related to the kind of the dye sensitizer and the number of dye molecules adsorbed on the photoanode. The electron collection efficiency is mainly influenced by the photoanode material, electrolyte and catalytic activity of the counter electrode. The electron injection efficiency is mainly related to the band gap of dye sensitizer and photoanode, and it is also related to the deposition state of the dye molecules on the surface of the photoanode. In this paper, two kinds of photoanode structure were designed to improve the electron transfer rate, reduce the probability of recombination, improve the electron injection efficiency and achieve the ultimate goal of PCE. The main researches of this paper as follows:1. An efficient photoanode consisting of indium-tin-oxide(ITO) conductive thin layer-filled titanium dioxide(TiO2) mesoporous photoanode is fabricated in DSSCs. Effects of ITO interlayer in photoanode on the photovoltaic performance of DSSCs are mainly investigated by means of incident photo-to-current efficiency(IPCE) spectra, electrochemical impedance spectroscopy(EIS) and current density-voltage(J-V) curves. Test results show that ITO nanoparticles act as an electron sink of photo-induced charge carriers for the improvement of interfacial charge transport, thereby resulting in the significant increase in the power conversion efficiency of DSSCs. Compared with the reference DSSCs without ITO interlayer, the ITO interlayer based DSSCs shows a 15.06% improvement of power conversion efficiency.2. γFe2O3 is a wide band gap semiconductor oxides. A TiO2 mesoporous layer mixed with a percentage of γFe2O3 magnetic nanoparticles(TiO2/γFe2O3) used as electron extraction layer in DSSCs. Magnetized TiO2/γFe2O3 photoanode could produce a local weak magnetic field(-20 Gauss), which gives a 21.23% enhancement in the power conversion efficiency when compared with the unmagnetized TiO2/γFe2O3 device. As an invisible bridge, a weak magnetic field could effectively inhibit the charge recombination reaction during electron transport through the photoanode based on the results of EIS, intensity modulated voltage spectroscopy(IMVS) and photoluminescence spectrum(PL). Besides, the residual magnetism effect could induce the strong spin-orbit coupling from the ruthenium heavy atom center, which cause an increase in the population of triplet states relative to singlets states. This change would lead to a higher net efficiency of charge dissociation from excited dye molecules and further improve the charge injection performance.