Low-cost selective deposition of wax onto textured solar cells

Abstract

The active regions of a solar cell must be inoculated with wax, while leaving the metal fingers and bus bars bare, in preparation for the electroplating step of a new solar panel manufacturing process. Different methods to achieve the inoculation of the cell are discussed, along with their advantages and disadvantages. A proposed solution is presented, along with results from test runs. The methods use a new feature of solar cells-microscopic, light-trapping textures-to passively wick the liquid wax to the extents of the regions through capillarity. Using this self-aligning feature of the cell texture, a low-cost delivery device was designed to bring liquid wax beads to within close proximities of the surface, without requiring high-precision equipment. The prototype uses an array of pins of diameter 1 mm, each of which beads a repeatable amount of wax on its head (- 0.1 mg), to transport the liquid wax from reservoir to cell texture. No metal-to-wafer contact is done in the process. The design has been used as a basis to create a machine at the Photovoltaics Laboratory (PV Lab). Successful inoculation of monocrystalline solar cells has been achieved using the proposed method.