NREL Develops Efficient Midgap Solar Cell

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Description and Advantages

A collaborative effort between NREL's Amorphous Silicon Team and United Solar Systems Corporation (Uni-Solar) has produced an efficient midgap solar cell whose active layer—a-SiGe:H alloy—is deposited at the high rate of 10 Å/s using the hot-wire chemical vapor deposition (CVD) technique. A power of 4.2 mW/cm2 was measured through a 530-nm cutoff filter, which means that this cell would contribute about 4.2% as the midgap middle cell in a 12%- to 14%-efficient triple cell. Uni-Solar's best 6 Å/s midgap cell delivers 4.4 mW/cm2 . This new result shows the potential of fabricating high-efficiency tandem or triple-junction amorphous silicon solar cells at higher deposition rates, an important result for low-cost production of PV modules. The delivered power of 4.22 mW/cm2 is an active-area measurement, with a short-circuit current density (Jsc) of 8.05 mA/cm2 after correction by quantum efficiency measurement. The fill factor (FF) is 0.69 and the open-circuit voltage (Voc) is 0.76 V. Light soaking of this cell to determine its stabilized efficiency is under way.


Application

Production of Photovoltaics modules and high-efficiency tandem or triple-junction amorphous silicon solar cells.


Source

National Center for Photovoltaics: http://www.nrel.gov/ncpv