| In the development of third generation photovoltaic technology sensitized mesoscopic solar cells (MSC) have a leading edge over other technologies due to their lower cost, simple fabrication methods and high power conversion efficiencies. Up to now, the highest certified power conversion efficiency (PCE) of the dye sensitized soalr cell (DSC) and perovskite solar cell (PSC) are 11.9% and 21.3%, respectively, which is comparable to that of the traditional Si version.Interface modification is one of the most important approaches to improve the cell performance of MSC. In this paper, we employed Cu2ZnSnS(Se)4 (CZTS(Se)) and Ni1-xMgxO as interfacial modification materials in MSC to obtain improvement of performance. The research is focused on the interaction between interface modification material and sensitizers, electrolyte, counter electrode and their effect on the photovoltanic propetties of MSC. The main results and conclusion of this disertasion are as follows:Firstly, lost-cost counter electrodes (CEs) based on CZTS(Se) nanoparticles (NPs) have been successfully introduced to quantum dot-sensitized solar cells (QDSC). The investigation has demonstrated that the catalytic activity of CZTS(Se) based CEs is sensitive to the composition and thermal annealing condition. The CZTSe CE with porous structure, fabricated by spray deposition method and sintered at 450℃ in Argon atmosphere, exhibits an excel PCE of 4.35% under AM 1.5 solar (100 mW cm-2) irradiation in a QDSC, which is about 70% higher than that of device using the conventional thermally platinized conducting glass CEs.Secondly, as an extended research, in this paper, we designed a multiwall carbon nanotubes (MWCNT)-CZTSe composite CE with the purpose of taking advantages of both components, namely, good conductivity of the one-dimensional MWCNT acting as fast electron transfer pathways and high catalytic activity of CZTSe nanoparticles with large surface area promoting electron exchange at the catalyst/electrolyte interface. With this purpose in mind, QDSCs based on composite CEs with different MWCNT-CZTSe weight ratios have been comparatively studied. Suitable surface modification allows MWCNT and CZTSe NPs be homogeneously dispersed in water, facilitating the subsequent low-temperature spray deposition of high quality composite films with different composite ratios. The best performance was finally achieved at the MWCNT: CZTSe ratio of 0.1, with the optimal efficiency of 4.6%, much superior to the CEs made of each single component and the Pt reference. The as-demonstrated higher catalytic activity of composite CEs than their single components is suggested be ascribed to the combination of fast electron transport of MWCNT and high catalytic activity of CZTSe NPs.Thirdly, a series of Ni1-xMgxO (x=0-0.2) oxides mesoporous films with p-type semi-conductivity prepared by surfactant directed self-assembly method have been successfully applied as photocathodes in p-type DSC system. By gradually increasing Mg content from 0 to 20% in the ternary oxides, the effective light harvesting efficiency increases monotonically which is associated with the increased dye absorbing amount and improved optical transmittance, meanwhile the flat-band potential gradually increases, implying a continuous negative shift of valance band position of the p-type semiconductors. The latter is closely related to the charge injection from dye to semiconductor and the photovoltage (Voc) of the solar cell. The overall PCE is optimized at the Nio.9Mg0.1O photocathode, which is significantly improved by about 85% from pure NiO. The enhanced performance is attributed to 34.4% increased photocurrent density (Jsc),22.5% increased Voc, and 13.0% increased fill factor. These improvements can be explained by increased light harvesting, enhanced charge collection, and flat-band potential positive shift. Further increasing Mg content in the ternary oxide to be Ni0.8Mg0.2O, the valance band position is too deep to hinder efficient hole injection. Jsc of the corresponding solar cell decrease largely. This work proves that Ni0.9Mg0.1O is a superior alternative to NiO as photocathode material in p-type DSCs.Fourthly, Ni1-xMgxO ternary oxide was synthsised by a citric acid-nitrate combustion method. Given that the energy band position will be turned related to different Ni/Mg moral ratio, we design to elmploy Ni1-xMgxO as metal oxide scaffold for TiO2/ZrO2/C type perovskite soalr cell. Replacement part of ZrO2 by Ni1-xMgxO led to 20% increase of energy conversion efficiency of hole-conductor-free organometallic perovskite solar cell based on carbon electrode. By employing a drop-casting method to infiltrate the perovskite CH3NH3PbI3 into the porous TiO2/ZrO2/Ni1-xMgxO/C layers, we achieved a power conversion efficiency of 13.6%. |
