Harnessing the sun with thin-film photovoltaics

Photovoltaic (PV) technologies have a substantial role in meeting electric power needs in the next century, especially with an expected competitive position compared to conventional power-generation and other renewable-energy technologies. Thin-film photovoltaic modules based on CdTe, CuInSe2 or Si can potentially be produced by economical, high-volume manufacturing techniques, dramatically reducing component cost. However, the translation of laboratory thin-film technologies to first-time, large-scale manufacturing has been much more difficult than expected. This is due to the complexity of the processes involved for making large-area PV modules at high rates and with high yields, and compounded by the lack of a fundamental scientific and engineering base required to properly engineer and operate manufacturing equipment. In this paper, we discuss the need to develop diagnostics tools and associated predictive models that: quantitatively assess processing conditions and product properties. Incorporation of the diagnostic sensors into both laboratory reactors and manufacturing facilities will (1) underpin the development of solar cells with improved efficiency, and (2) accelerate the scale-up process through intelligent process-control schemes. "Next-generation" high-performance (e.g., >25% conversion efficiency) thin-film PV modules will also be assessed, along with critical issues associated with their development.