Fabrication And Characterization Of Photo-anode Materials Used In CuInS₂-sensitized TiO₂ Solar Cells

The development of the solar cells were reviewed in this paper based on the comprehensive utilization of soalr cells. The material and the structure of different kinds of the solar cells and the problems were expatiated. The thought, that is using CuInS₂-sensitized TiO₂ solar cells, was put forward.Titanium dioxide (TiO₂) is a kind of cheap, safe and wide application range semiconductor material of solar cells. But it can not absorb the solar radicalization effectively for its wide band-gap (3.2 eV). One way to solve this problem is to sensitize it to increase the transformation efficiency. Organic dye sensitized solar cells (DSSC) have been an active research project since 1991. But organic dye has disadvantages such as high cost, short age and unstable performance. Now, using inorganic semiconductor sensitizer to substitute organic dye has been a new research in the soalr cells field.As aâ… -â…¢-â…¥₂ ternary semiconductor compound, copper indium disulfide (CuInS₂) can be applied to fabricate solar cells, whose absorption coefficient is reached to 10⁴-10⁵ cm^-1. Its direct band gap is 1.50 eV which is close to the best band gap of the solar cell materials (1.45 eV). In comparison with CuInSe₂, CuInS₂ is an environmentally benign material with no toxic composition, and it is a kind of promising solar cell material. But there are some primary problems as complicated manufactural process and high cost that counteract the practicality of CuInS₂ solar cell. Hence, a simple and low cost method is needed, urgently. In this paper, the controllable synthesis and characterization of CuInS₂ were studied.Three main parts were involved in this study: the synthesis of CuInS₂ particles by solvothermal method was introduced in the first part, the preparation of CuInS₂ films by successive ionic layer absorption and reaction method (SILAR) is depicted in the second part and the investigation of the TiO₂/ CuInS₂ photoanode is presented in the last part. And the samples were characterized by XRD,FESEM,EDS,TEM,SAED and UV-vis.The controllable CuInS₂ particles were synthesized by solvothermal method and the effect of different kind of solvent, different ratio of reagents, reaction temperature, reaction time, filling factor, pH value and surfactant on CuInS₂ particles were investigated. The optimum parameter was as follows: choose ethylene glycol as solvent, the ratio of reagents was Cu: In: S=1: 1: 4, reaction temperature was 150℃, reaction time was 6 h, filling factor was 80 % and the surfactant was polyvinyl- pyrrolidone (PVP).The CuInS₂ films prepared by SILAR method can meet the requirement of the absorbing layer material for solar cells. But the films did not be protected by inert gas, and could be oxidized easily during the cycle process. The surface of the films was not very smooth, which could cause the band gap broadened.The absorbance of the TiO₂ electrode which was sensitized by CuInS₂ particles was better than the insensitized electrode, obviously. And its absorption edge was red-shifted to 800 nm, which could absorb visible light mostly. The band gaps of the electrode material which were sensitized by different size of CuInS₂ particles were from 1.54 to 1.72 eV. This can meet the requirement of solar cells. But the transformation efficiency is low, which needs to further study.