Process Development for CIGS Based Thin Film Photovoltaic Modules: Final Technical Report, 5 February 1998-4 February 2001

Global Solar Energy initiated an extensive and systematic plan to accelerate the commercialization of thin-film photovoltaics (PV) based on copper indium gallium diselenide (CIGS). The distinguishing feature of the GSE manufacturing process is the exclusive use of lightweight, flexible substrates. GSE developed the technology to fabricate CIGS photovoltaics on both stainless-steel and polymersubstrates; over the course of the Thin Film PV Partnership program, however, stainless steel showed significant advantages. CIGS deposited on flexible substrates can be fabricated into either flexible or rigid modules. Low-cost, rigid PV panels for remote power, bulk/utility, telecommunication, and rooftop applications have been produced by affixing the flexible substrate to an inexpensiverigid panel by lamination or adhesive. There have been numerous challenges in developing the technology for manufacturing flexible CIGS photovoltaic modules. Three major areas deemed exceptionally challenging were selected by GSE for focused development under the Thin Film PV Partnership Program: 1) CIGS absorber improvement, 2) monolithic integration, and 3) encapsulation. Most conventionaltechniques for monolithic integration of thin film PV devices on glass substrates cannot be applied to integrate devices on a polyimide substrate. Novel interconnect schemes and processes had to be developed. The encapsulation of a flexible module also presented special problems to solve, and unique advantages to employ.