Research On CIGS Thin-Film Solar Cell Made By Magnetron Sputtering

The CuIn_1-xGa_xSe₂(CIGS) semiconductors are considered as the most promising candidates for application as an absorber in the CIGS thin film solar cells because of high efficiency, the most excellent long-term stability, high radiation hardness and low lost. The main preparation methods are co-evaporation, post-deposition selenization, electro-deposition and spray pyrolysis. However, there are a lot of problems for large scale production as the complex CIGS structure and a higher crystallization conditions.This work presents the results of investigation of preparation of CIGS thin film solar cells by magnetron sputtering. The sputtering pressure, power, temperature and annealing temperature are investigated to fabricate absorber (CIGS thin films), buffer layer (ZnS thin films) and window layer (ZAO thin films) on the glass substrates separately. The crystalline structure, surface morphology and composition ratio of the thin films were characterized by XRD, SEM and XRF.We present the structural and electronic characterization of CuInGaSe₂ (CIGS) and CuInAlSe₂ (CIAS). The fully-relaxed calculations have been made using the density functional theory, and structure constant matches the experimental values. The density of states, adsorption constant, reflectivity, dielectric constant and refractive index are also calculated. Our results show that the chalcopyrite CIGS and CIAS are direct band gap semiconductors with band gaps 1.34eV,1.50eV respectively. Comparatively, CIAS have higher adsorption and dielectric values with lower reflectivity at high photon energies, which is promising for high efficiency solar cells.The composition and the structure of CIS thin films are greatly influenced by the working power and annealing temperature, separately. The prepared sample demonstrates good chalcopyrite crystal structure and uniform surface image after 560℃annealing compared of 580℃annealing. The CIGS thin films were prepared by co-sputtering using the CuIn, CuGa and Se targets. Also, the films present good chalcopyrite crystal structure and uniform surface image after 560℃annealing. But the composition of the films has a little deviation from CuIn_0.7Ga_0.3Se₂.We fabricated ZnS and ZAO on glass substrate separately. The crystal structure of ZnS is determined mainly by pressure and sputtering power. With the pressure increasing from 0.2Pa to 1.0Pa, the structure of the ZnS film turned from crystalline to non-crystalline. The electrical characteristics of ZAO film is influenced greatly by pressure, sputtering power and temperature. The light transmission rate of the ZAO films is almost above 80%.