PHOTOVOLTAICS TODAY

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ARCO's new module represents far more than just another item in a long line of successful products. It actually introduces a revolutionary change to the photovoltaics-manufacturing process. A Genesis panel is made by depositing a micro-thin layer of amorphous silicon on a sheet of treat ed window glass. The silicon is then exposed to various levels of chemical processing to form the all-important semiconductor junction, where sunlight is converted to electricity. Furthermore, unlike conventional solar panels, which require that the individual solar cells be wired together by hand, the Genesis module is manufactured as a solid unit. This advance is analogous to the transition from discrete transistors to integrated circuits in the electronics industry a few years ago.

All 25 of Genesis's cells—the number needed to generate 12 volts—are fabricated in a single process. Prior to the deposition of the amorphous silicon, a grid of conductive tin is laid down on the inside surface of the glass to serve as the connecting electrodes. The pattern of the grid is arranged in such a way that no two adjacent strips are touching. When the silicon is deposited on top of the tin, the photovoltaic junction is formed.

By the time the process is complete, the single pane of glass contains 25 contiguous solar cells. Finishing the module consists only of connecting the cells with another mask and applying aluminum alloy to the back of the cell. The drawing on page 77 shows the geometry of a Genesis module viewed from the edge. Remember as you look at it that the cells are laid down in strips; what you see are two adjacent cells.

This procedure has two advantages. First, manual labor is no longer required to connect the cells, so manufacturing costs are reduced. Second, because the interconnection between cells is an actual part of the solar cell forming process, there's less chance of something coming loose. Module reliability is improved.

Admittedly, ARCO Solar's Genesis is but a small step in the new direction. Higher-power modules might be the next stage. But Genesis is an important first step.

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