Abstract
Overall performance of a thin film solar cell is determined by the efficiency of converting photons to electrons through light absorption, carrier generation, and carrier collection. Recently, photon management has emerged as a powerful tool to further boost this conversion efficiency. Here we propose a novel nanograting solar cell design that achieves enhanced broadband light absorption and carrier generation in conjunction with the reduced use of active and non-earth-abundant materials. A test using this design for the short circuit current density in CuInxGa(1-x)Se2 (CIGS) thin film solar cells shows up to 250% enhancement when compared to the bare thin film cells. In addition, placing metal strips on top of the nanograting to act as the top electrode reduces the use of non-earth-abundant materials that is normally used as the transparent conducting materials. This novel solar cell design has the potential to become a new solar cell platform technology for various thin film solar cell systems.
Highlights
Thin film solar cell technology presents a powerful tool to tackle the world's increasing energy shortage problem
It is remarkable that when the nanowire width is 85 nm and the array period is 200 nm, with the CIGS thickness ranging from 70 to 95 nm, the total short circuit current generated by the CIGS nanograting solar cell can reach up to a 8% enhancement compared to its conventional counterpart, while using only 42.5% of the total absorbing material and eliminating the transparent top oxide electrode
When calculating the current density enhancement by averaging the absorption enhancement over the whole solar spectrum (Eq (4)), larger ηcon(λ) at long wavelength gave strong absorption enhancement, resulting in an enhanced current density. The absorption of this new nanograting solar cell design is dependent on geometric parameters, illumination conditions, and construction materials
Summary
Thin film solar cell technology presents a powerful tool to tackle the world's increasing energy shortage problem. A new thin film solar cell design, that is able to reduce the amount of active and non-earth-abundant materials, enhance and balance the full-spectrum absorption, and improve the overall conversion efficiency, would be of significant importance. Thin film solar cells use non-earth-abundant elements in two major areas, such as indium in CuInxGa(1-x)Se2 (CIGS) as an absorbing material and in indium tin oxide (ITO) as a surface electrode. Large scale implementation of the CIGS solar cells would benefit from new technologies that are able to reduce such nonearth-abundant material usage inside both the absorbing layer and the surface electrode layer without sacrificing the light absorption efficiency [24]. This design could be applied to many semiconductors such as a-Si, CdTe and GaAs, and will lead to a new solar cell platform technology
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