Key near-term R&D issues for continuous improvement in CIS-based thin-film PV modules

In a large-area approach up to 60 cm×120 cm size, monolithically integrated CIS-based thin-film PV modules have come to the efficiency level of 13%. The key near-term R&D issues to realize continuous improvement in CIS-based thin-film PV modules are related to their competitiveness against the crystalline-Si PV modules. In this contribution, the following three issues are discussed. The first and main issue is how important it is to understand the interfaces in the CIS-based thin-film circuit to improve the efficiency, because CIS-based thin-film circuits are fabricated in a stacked structure of four or five thin films. The second and third issues are how beneficial it is to develop the packaging and material recycle technologies in order to reduce the production cost.