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Micro Chiplet Printer for Microscale Photovoltaic System Assembly
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The micro-scale concentrated photovoltaic (micro-CPV) concept uses an array of micro-scale unit cells (or elements) such that the material usage, weight, and the required structural strength for photovoltaic systems can all be scaled down favorably. Unfortunately, one of the essential and unfavorable scaling factors is the assembly cost due to the many micro-scale components that must be deposited, positioned, oriented, and connected over large areas. PARC and Sandia are working together to create a capability to fabricate panel-sized micro-CPV modules using electrostatic micro-assembly. A general, massively parallel, high throughput micro-assembly tool that is based on the industrially proven xerographic process has been developed at PARC. In this digital manufacturing process, the \"inks\" are micron-scaled PV components that Sandia has developed and the \"image\" is the micro-CPV module itself. The process will enable large area out-of-the-box micro-CPV designs that are otherwise prohibitively slow and expensive using other assembly processes. To develop and demonstrate the fundamental capabilities needed, a 4×4 array of circular electrodes driven by 16 control amplifiers was built and used as an assembly tool test bed. In this paper, by using a dynamic electric field template, we successfully demonstrate chiplet printing - assembling a desired solar cell chip at a designated location with well controlled orientation. The technical milestones achieved include demonstration of: 1) a charge encoding and singulation process, 2) transportation and orientation by both fixed pattern electrodes and a 4x4 electrode array, 3) submicron positioning accuracy, 4) transfer and wiring, and 5) assembly of 150 x 150 um hexagonal solar cells produced by Sandia. These results support the conclusion that Xerographic printing systems utilizing this method can be extended to provide high-throughput, on-demand heterogeneous assembly of micro-CPV systems.