Fabrication And Characterization Of CuInS₂ Quantum Dots Sensitized ZnO Based Nanostructure Solar Cells

The simplicity of the synthetic procedure, tunability of light absorption, sensitivity to diffused light, and ability to design flexible solar panels make the semiconductor nanostructure an important candidate as a light absorber. Recently, there are three major types of next-generation solar cells fabricated by nanostructure architectures including dye-sensitized solar cells(DSSC), bulk heterojunction(BHJSC) photovoltaic cells, and quantum dot sensitized solar cells(QDSSC).CuInS2 semiconductor quantum dots are widely used in solar cells because of their excellent optical and electrical properties. The advantages of high electron mobility, higher bottom of the conduction band and easiness to control the morphological structure, make ZnO as a promising material for the QDSSC anode which can provide many possibilities to improve the efficiency of the cells. In this work, the purpose is to fabricate and characterize CuInS2 quantum dots sensitized ZnO based nanostructure solar cells; CuInS2 quantum dots and ZnO nanocrystals film were prepared, and CuInS2 quantum dots sensitized ZnO nanocrystalline photo-anode or solar cells were assembled and the performance was studied. The conclusions could be summarized as follows.Firstly, zinc-blende and wurtzite CuInS2 nanocrystals were synthesized successfully by heat up method. Zinc-blende CuInS2 quantum dots could be obtained at a low dosage of OA, while a mixture of zincblende CuInS2 nanoparticles and wurtzite CuInS2 nanoplates formed at a moderate dosage of OA. When the OA dosage was high, wurtzite CuInS2 nanoplates were produced but a part of them dissolved and transformed into new zinc-blende nanoparticles as the reaction proceeded. By the investigation on the growth mechanism of CuInS2 nanocrystals with different phase structures in detail, it is revealed that the dosage of OA can affect the state of CuIn(SR)x complex and nucleation rate of CuInS2 NCs, which determine the phase structure of NCs.Secondly, zinc-blende CuInS2 quantum dots with good dispersivity were synthesized by a hot injection method, and the size of the QDs was around 6 nm. ZnO nanorod arrays with different thickness were prepared by adjusting the growth time. CuInS2 quantum dots sensitized ZnO nanorod arrays anodic was prepared by depositing CuInS2 quantum dots on to the ZnO nanorod arrays with electrophoretic deposition method. Importantly, it is found that increasing the length of ZnO nanorods can increase the photocurrent of the anodic.Thirdly, ZnO nanotetrapods based film and the composite film of TiO2 and ZnO were prepared by screen printing method using the ZnO nanotetrapods paste and TiO2 P25 paste. CuInS2 quantum dots were adsorbed on the surface of ZnO in a self-assembly way by the connection of mercapto propionic acid(MPA) which is a bifunctional molecule. CuInS2 quantum dots sensitized TiO2 and ZnO composite film solar cells were fabricated, and it is found that the compositing of TiO2 and ZnO can increase the short circuit current, but reduce the open circuit voltage. The open circuit voltage could be increased after the composite film was treated with TiCl4 aqueous solution. ZnS passivation layer was deposited on the surface of CuInS2 quantum dots by SILAR method, which can improve the short circuit current of the solar cells.