106 Thin Crystalline Silicon Photovoltaics Simulations

Wednesday, November 4, 2009: 11:40 AM
Charolais (Camino Real Hotel)
Jose Luis Cruz-Campa , MEMS, Sandia National Laboratories, Albuquerque, NM
Murat Okandan , MEMS, Sandia National Laboratories, Albuquerque, NM
Tammy Pluym , MEMS, Sandia National Laboratories, Albuquerque, NM
Paul Resnick , MEMS, Sandia National Laboratories, Albuquerque, NM
Ralph Young , MEMS, Sandia National Laboratories, Albuquerque, NM
Robert Grubbs , MEMS, Sandia National Laboratories, Albuquerque, NM
Gregory N. Nielson, PhD , Advanced MEMS Group, Sandia National Laboratories, Albuquerque, NM
Over the last decade, thin (< 50 mm) crystalline silicon photovoltaics have been of significant interest to the research community. Crystalline silicon is able to absorb most of the solar spectrum within a few tens of microns of optical path length.  Thin silicon solar cells provide reduced cost (through materials savings), lighter weight, and higher open circuit voltages. Sandia National Laboratories has introduced an innovative way to create ultra-thin, small form factor (sub-millimeter), crystalline silicon solar cells, using concepts from microsystems and MEMS. In this talk, key results from simulations of these devices will be presented and discussed.  Tsuprem4 and Medici (both software by Synopsis) were used for these simulations. A variety of different designs was explored under one-sun and concentrated light scenarios to understand the design space for these ultra-thin c-Si PV cells. Several variables (e.g., surface recombination, bulk recombination, doping concentration, and thickness of the solar cell) were tested, with direct effects on performance. Due to the high surface area to volume ratio of these ultra-thin cells, surface parameters dominated the behavior of the solar cell. Varying these parameters raised conversion efficiency from < 1% to 18%.  Finally, the simulations with varied surface recombination values were compared to experimental results of actual cells, where a variety of surface passivating films were explored.  Simulated results were consistent with experimentally measured values.