Abstract
Light trapping nanostructures offer the potential to increase solar cell efficiencies while dramatically reducing the semiconductor volume. Integrating designed nanostructured surfaces and three-dimensional architectures offer the potential to manipulate and direct light to specific locations in the semiconductor, with potential for novel device designs. For amorphous Si (a-Si:H) based solar cells, randomly roughened surfaces are a standard part of commercial fabrication.
Here we use designed arrays of plasmonic nanoparticles as the back contact and growth substrate for a three dimensional, ultrathin a-Si:H solar cell. We form the patterns using nanoimprint lithography, an inexpensive and scalable method. Each successive layer of the device deposits conformally, resulting in a three-dimensional final structure which exhibits broadband light trapping across the portion of the solar spectrum where a-Si:H is active. We fabricated devices with 90 nm, 115 nm, and 150 nm thick intrinsic layers.
The shape and arrangement of Ag particles is carefully controlled and is based on parameters from electromagnetic simulation, which agrees well with experiment. Notably, the measured photocurrent on the blue side of the spectrum is dramatically enhanced for particular patterns over randomly textured references, and we show that this is due to weakly coupled Mie scattering from the top a-Si:H/ITO features. Photocurrent enhancement in the green and red portions of the spectrum is due to localized and guided modes excited by scattering from the plasmonic nanostructures on the back of the semiconductor. We studied a variety of different nanoparticle lattices, including periodic, quasi-periodic, and pseudo-random tilings, and randomly textured references. By engineering the spatial frequencies present in the lattice to match to the modes of ultrathin film a-Si:H, we are able to achieve efficiencies over 9.5% with intrinsic layers less than 100 nm. These designer patterns also show isotropic angular response.
Original language | English |
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Publication status | Published - 19 Jun 2011 |
Event | 37th IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE - Seattle, Washington Duration: 19 Jun 2011 → 24 Jun 2011 |
Conference
Conference | 37th IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE |
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City | Seattle, Washington |
Period | 19/06/11 → 24/06/11 |