Solar photovoltaic (PV) energy conversion is a technically viable and sustainable solution to society's energy needs, but the costs must be further reduced for widespread adoption. Hydrogenated amorphous silicon (a-Si:H) is an inexpensive and readily available earth abundant solar cell material, which stands to revolutionize our capability for generating clean sustainable energy. PV cells made with a-Si:H have the fastest energy payback time of any commercial PV device and are therefore the most useful for combating climate change. Unfortunately, the light induced degradation of the electronic properties of a-Si:H limits their overall efficiency.
This project envisions that the metamaterial paradigm will allow for managing light from the sun for photovoltaic conversion more efficiently than is theoretically possible with traditional optical enhancement. For example, solar light impinging on a metal surface produces waves along the surface when it interacts with the collective oscillations of free electrons in the metal. These surface waves referred to as surface plasmon polaritons, can be exploited to make plasmonic metamaterial ?perfect absorbers? (plasmonic perfect meta-absorbers) to enhance the efficiency of solar PV devices. Perfect meta-absorbers can be designed with broadband, polarization-independent, and wide-angle optical absorption features. These critical features, lacking in most optical enhancement schemes for solar cell designs, are ideally required to maximize the efficiency of solar cells. Wide-angle reception, for example, is particularly important to increase solar energy conversion efficiency for curved surfaces, and for maximized temporal and spatial response of the panels to solar light.
In this project, a plasmonic perfect meta-absorber will be optimized for maximum solar energy conversion efficiency. High conversion efficiency will be derived from polarization-independent operation over the entire solar spectrum with a wide-angle reception. This absorber will be integrated with a-Si:H PV device and shown how to focus the optical absorption to the desired semiconducting regions to significantly enhance the overall conversion efficiency. Additionally, it will be possible to make ultra-thin solar cells using these absorbers.
The optical enhancement will directly reduce the effects of Staebler-Wronski Effect in the cells by allowing their thicknesses to be decreased. This will result in the reduction in the levelized cost of electricity of a-Si:H PV by two means: 1) reduction in initial cost because of higher throughput from thinner i-layers and 2) improved energy conversion efficiency from enhanced light capturing. The concept in this proposal can be also extrapolated to ultra-high efficient/sensitive photodetectors/sensors tunable over THz through UV frequencies. Additionally, this project will provide professional and intellectual training for two graduate students in an academic and industrial collaborative environment.
