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IPFS News Link • Energy

Progress to Higher Efficiency Thin Film Solar Cells

•, by Brian Wang

AMOLF group leader Esther Alarcon Llado says: "based on the strong light trapping performance of our patterns, we estimate that PV efficiencies above 20% could be achieved for a 1 μm-thick c-Si cell, which would represent an absolute breakthrough toward flexible, lightweight c-Si PV.

Also, thinner Si absorbers are more tolerant to electronic defects compared to the thick counterparts. This means that thin Si cells with high efficiency could also be made from lower grade Silicon, thereby reducing the energy needs for raw Si purification and reducing their energy pay-back time. Hyperuniform patterned thin PV is a highly promising technology. While there is still plenty of work to be done to make such thin high efficiency cells part of our living environment, this work makes us very optimistic that this will happen soon."

Over 65% Sunlight Absorption in a one micron Si Slab with Hyperuniform Texture

Thin, flexible, and invisible solar cells will be a ubiquitous technology in the near future. Ultrathin crystalline silicon (c-Si) cells capitalize on the success of bulk silicon cells while being lightweight and mechanically flexible, but suffer from poor absorption and efficiency. Here we present a new family of surface texturing, based on correlated disordered hyperuniform patterns, capable of efficiently coupling the incident spectrum into the silicon slab optical modes. We experimentally demonstrate 66.5% solar light absorption in free-standing 1 μm c-Si layers by hyperuniform nanostructuring for the spectral range of 400 to 1050 nm. The absorption equivalent photocurrent derived from our measurements is 26.3 mA/cm2, which is far above the highest found in literature for Si of similar thickness. Considering state-of-the-art Si PV technologies, we estimate that the enhanced light trapping can result in a cell efficiency above 15%. The light absorption can potentially be increased up to 33.8 mA/cm2 by incorporating a back-reflector and improved antireflection, for which we estimate a photovoltaic efficiency above 21% for 1 μm thick Si cells.

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