Synthesis and low-temperature sintering of CuInSe₂-CuGaSe₂ powders

A solar cell with a compound semiconductor CuInSe₂-CuGaSe₂ (CIGS) battery fabricated using the thin film process has weak points in that the unit cost is high and the process is complicated. To solve these problems, the screen printing method, a process for manufacturing the wide-absorbing layer of a I-III-VI2 compound semiconductor solar battery with ease and low cost, has been researched. Synthesis of a nano-sized homogenous CIGS powders is needed for firing of thick film formed at low temperature, and for this, the solvothermal method has been adopted. However, present, it's difficult to obtain accurate CIGS composition, and phase uniformity for mixtures of CIS, CGS, and CIGS has been obtained. In this study, homogenous CIS and CGS powders were synthesized by using the solvothermal method with CuCl, InCl, GaCl, and Se powders and diethylamine solvent. The paste for screen printing was prepared by mixing CIS and CGS powders whose sizes were about 0.3 μm and the CIGS layer was formed by using a printing process and firing. As a result, it's confirmed that CuIn_0.7Ga_0.3Se₂ was formed at 900 °C and that volatilization of Se ions was controlled by using Se powder at atmospheric pressure during the sintering.