Control of temperature uniformity during the manufacture of stable thin-film photovoltaic devices

The production of stable thin-film photovoltaic cells requires tight control of temperature uniformity within the glass substrates during the vacuum deposition process. Though traditional approaches such as radiation shielding and channeling more power to outer lamps result in substantial improvements in temperature uniformity they fail in meeting the stringent requirement of less than 1 °C variation across the substrate required to guarantee the long-term stability of the devices. The problem becomes especially acute while scaling up to larger commercially-viable panel sizes. To this end, a finite element thermal model of a commercial-scale deposition station has been developed and optimized with the target of achieving the desired temperature uniformity of 1 °C. The effects of improvements such as radiation shielding, addition of radiation spreader, contouring of radiation spreader and optimizing power distribution among the radiation lamps have been studied. A new lamp configuration has been proposed for attaining the desired uniformity levels.