Flexible Solar Cells and Stable High-Efficiency Four-Terminal Solar Cells Using Thin-Film Silicon Technology

Amorphous silicon (a-Si:H) materials are used in diverse applications such as in active matrix displays, solar cells etc. These types of devices are constructed as multilayers in a multichamber (or cluster tool) system to avoid cross contamination. In this, each process chamber is separated from others via gate valves leading to optimal performance of an electronic device. The planar substrate, such as glass, is transported via a robotic arm from one chamber to another. We present a new type of system architecture to manufacture electronic devices (thin film silicon transistor and solar cells) on flexible substrates, and propose a reel-to-reel cassette suitable for use in a cluster tool system. We report on the development of flexible thin-film silicon solar cells fabricated on low-cost plastic substrates, which can have major applications in buildings to replace tinted glass. We also report on stable amorphous Si and nano-crystalline Silicon (nc-Si) tandem junction solar cell constructed as a four-terminal (4-T) device, in which the current matching constraint is released from each constituent cell. By merely joining two cells constructed on separate pieces of glass, we have achieved conversion efficiency, η > 9%. We show that by constructing the 4-T device on either side of the glass or plastic, η > 12% can be achieved. Lastly, we discuss the use of pulsed PECVD technique which should be able to improve the properties of nc-Si material thus providing a road map to η > 16% on rigid and flexible substrates.