Scaling Up Issues During Application of Large Size Cu(In,Ga)(Se,S)(2) Solar Module

Abstract

Polycrystalline Cu(In, Ga)(Se, S)(2) (CIGSSe) thin film solar modules have significant potential for improved efficiency and reduced production costs. Such cell with an efficiency of about 22.3% was reported in Japanese Company. This efficiency approaches the best efficiency that has been achieved with multi-crystalline silicon solar cells. In addition, CIGSSe based thin film solar cells feature excellent low light behavior, outdoor power generation, and light absorption characteristics. However, there is still a significant gap between the efficiencies of small cells made in laboratory and those of large modules made via mass production, even though many companies have studied mass production technology. Therefore, further manufacturing technology development is necessary to achieve high efficiencies in mass production. We have investigated technologies for mass production of large (16 x 90 cm(2)) CIGSSe modules fabricated via a two-step sputter and selenization/sulfurization method with Cd-free buffer layer. We have focused on film homogeneity over the area of the solar cell, the bottom electrode, and the absorber layer. In addition, we have optimized formation of the absorber layer and transparent conducting oxide layer, as well as the monolithic pattern design. The resulting improvements in module power come from better thin film uniformity and an optimized the monolithic pattern design.