Application Of Rare-earth Doped Oxides In Dye-sensitized Solar Cells Based On Zn₂SnO₄ Photoanode

Dye-sensitized solar cell has been paid extensive attention for its low cost,low pollution and high efficiency.Now N3 and N719 are usually used as sensitizer for DSSC.The sensitized photoanodes mainly absorb visible light,but little ultraviolet and infrared light.However,the oxide doped with rare-earth can function as a conversion luminescent agent,which is capable to convert ultraviolet or infrared light unabsorbed by DSSC to visible light through its down or up conversion.This extends spectral response range of DSSC and improves efficiency for solar energy utilization,which increases the photoelectric conversion efficiency.Zn2SnO4 with the anti-spinel structure has the characteristics of fine photocatalytic activity and wide band gap.In this work,different oxides were used as matrix for rare-earth doping to synthesize luminescent materials with down or up conversion.Then the luminescent material and nano Zn2SnO4 were manufactured as photoanode of DSSC,which enhanced the photoelectric conversion efficiency.The main achievements are as follows:(1)Zn2SnO4:Sm3+ particles with truncated octahedron were synthesized by hydrothermal and heat treating method.Then the particles were prepared as down-conversion membrane photoanode,and the impacts of rare-earth dopant concentration on the photovoltaic performance of DSSC assembled with the photoanode were investigated.The Zn2SnO4:Sm3+photoanode could convert ultraviolet into visible light reused by N719.Besides,the density of defect was altered after doping.These reasons contributed to the improvement of Jsc-When the molar content of Sm3+ was 0.4%,the cell obtained the best photoelectric conversion efficiency,which was increased by 78%compared with the pure photoanode.(2)Yb2O3:Ho3+ was synthesized by solid reaction sintering method.The powders could absorb infrared light and generate green and red emission.The impacts of Ho2O3 concentration and pump power on the fluorescence intensity were studied.The particles exhibited better fluorescence performance when the mass percentage of Ho2O3 was 5%.Then the up-conversion material was mixed with nano Zn2SnO4 to manufacture photoanode,and the efficiency of DSSC was increased by 28.9%compared with the pure photoanode.This was because the up-conversion powder enhanced light-harvesting of the dye.(3)Zn2SnO4 particles with octahedron were synthesized by hydrothermal method,then the powder was used as reactant to produced Zn2SnO4:1mol%Ho3+,2mol%Yb3+ through the solid reaction sintering method.The impact of temperatures of solid reaction on the fluorescence intensity was investigated.When the temperature was 1000?,Zn2SnO4:lmol%Ho3+,2mol%Yb3+ revealed the best fluorescence performance.Then it was mixed with nano Zn2SnO4 to manufacture photoanode and assembled DSSC,and the efficiency of DSSC achieved 3.16%increased by 12.1%compared with the pure photoanode,which was attributed to the increasement of Jsc after doping.