Proceedings Article | 7 May 2012
KEYWORDS: Solar cells, Semiconducting wafers, Silicon, Photovoltaics, Gallium arsenide, Crystals, Indium gallium phosphide, Silicon films, Thin films, Solar energy
Current solar power systems using crystalline silicon wafers, thin film semiconductors (i.e., CdTe, amorphous Si, CIGS,
etc.), or concentrated photovoltaics have yet to achieve the cost reductions needed to make solar power competitive with
current grid power costs. To overcome this cost challenge, we are pursuing a new approach to solar power that utilizes
micro-scale solar cells (5 to 20 μm thick and 100 to 500 μm across). These micro-scale PV cells allow beneficial scaling
effects that are manifested at the cell, module, and system level. Examples of these benefits include improved cell
performance, better thermal management, new module form-factors, improved robustness to partial shading, and many
others. To create micro-scale PV cells we are using technologies from the MEMS, IC, LED, and other micro and nanosystem
industries. To date, we have demonstrated fully back-contacted crystalline silicon (c-Si), GaAs, and InGaP
microscale solar cells. We have demonstrated these cells individually (c-Si, GaAs), in dual junction arrangements
(GaAs, InGaP), and in a triple junction cell (c-Si, GaAs, InGaP) using 3D integration techniques. We anticipate two key
systems resulting from this work. The first system is a high-efficiency, flexible PV module that can achieve greater than
20% conversion efficiency and bend radii of a few millimeters (both parameters greatly exceeding what currently
available flexible PV can achieve). The second system is a utility/commercial scale PV system that cost models indicate
should be able to achieve energy costs of less than $0.10/kWh in most locations.
