Flexible cells and modules produced using roll-to-roll electroplating approach

Thin film Cu(In,Ga)Se₂ (CIGS) photovoltaic cells are considered to have a high potential for low cost electricity production due to their demonstrated high conversion efficiencies. Various methods have been used to make thin film CIGS solar cells. In the present approach, a low cost roll-to-roll electroplating process is utilized to deposit the CIGS precursor layers. The electroplating technology provides well controlled composition along the length and width of the flexible substrates demonstrating its suitability as a low cost CIGS precursor deposition method. Precursor layers are then subjected to rapid thermal processing to form a photovoltaic-grade CIGS absorber. The processing is done using roll-to-roll production equipment on a flexible metallic substrate. The CIGS based solar cells are fully finished in roll form and then cut into large area cells. The cells are then interconnected to fabricate panels with about 1.1 m² aperture area and about 115W power output. These rigid panels show excellent stability under damp heat test conditions and are certified against both UL and IEC standards. More recent work has focused on lightweight flexible solar modules. These modules open new application areas and can further lower the cost of systems by lowering the installation costs. Flexible modules with aperture area efficiency as high as 11.2 % have been demonstrated. Standard module certification tests, including 1000 hour damp heat test, show very small changes of Pmax.