Preparation And Characterization Of CdS Thin Films And HIT Solar Cells

In the severe energy situation and worsening ecological environment, changing the energy structure and developing sustainable green energy have become the theme of the world. As clean new energy, the solar cell has got great development. CdS/CdTe thin film solar cells have received wide attention in the field of photovoltaic owing to their high conversion efficiency, good stability and simple preparation method. As the window material of the CuInGaSe thin film solar cells, Cadmium sulfide (CdS) thin film plays an important role in improving the quality of p-n junction and cell performance. Besides, because of high efficiency and low cost, the heterojunction with intrinsic thin layer (HIT) solar cells also caused wide attention around the world. The highest efficiency of the HIT solar cells were prepared by Sanyo. Sanyo owns the most advanced technology in this field.This thesis includes two parts. The first part includes the preparation of CdS thin films by chemical bath deposition and their performance study. The second part includes the heterojunction interface passivation of HIT solar cells, the preparation of Indium tin oxide (ITO) transparent conductive films and optimization of solar cell process parameters.As an interesting II-VI group n-type semiconductor material, CdS film is the best choice of window layer in CuInGaSe and CuInSe thin film solar cells. The film quality directly affects the photoelectric conversion efficiency, stability and service life of the solar cells. In this experiment we prepared CdS thin films in the alkaline chemical bath and studied the effect of different bath temperatures and deposition time on the properties of them. Using X-ray diffractometer, scanning electron microscope, atomic force microscopy, UV-VIS-NIR spectrometer, Hall Effect Measurement System and Profilometer studied the structure, surface morphology, optical and electrical properties of the CdS thin films. The crystallization of CdS thin films has strong preferred orientation. The transmittance of deposited CdS thin films were all above75%at different deposition temperatures, and the transmittance varies with the deposition temperatures. CdS thin films deposited at70℃own the best surface topography. The values of optical band gap are in the range of2.34to2.48eV.In the second part, we studied the influence of different ways on HIT solar cell heterojunction interface passivation, and also the preparation of transparent conductive film. Meanwhile, by varying the hydrogen dilution degrees during depositing hydrogenated amorphous silicon layer on the crystalline silicon, the time of hydrogen plasma treatment and processing time in dilute HF, the effects of the three methods on their performances of HIT solar cells were studied. Then we studied the influence of different preparation conditions on transparent conductive films, and tested the optical and electrical performances of the films. The optimal process parameters as follows:the optimal flow of hydrogen is60sccm, hydrogen plasma treatment time is200s, and2%diluted HF processing time is40s. The best ITO thin films sputtering power is70W; sputtering pressure is2mTorr, and the prepared ITO thin films have high transmittance and excellent electrical performance under these conditions. The highest conversion efficiency of prepared HIT solar cell is9.6%.