(153e) Template Stripped Metal Nanostructures for Photovoltaics

Traditional solar cell absorber materials need to be optically thick in order to completely absorb the incident radiation that is above the band gap of the absorber. This results in absorber thicknesses of a few microns for highly absorbing direct band gap materials such as CdTe to several hundred microns for weakly absorbing indirect band gap materials such as crystalline silicon. Advanced photon management via nanostructured back reflector surfaces can facilitate light trapping, anti-reflection and plasmonic effects which allow for equal or better absorption with less material.  Reducing the thickness of the absorber layer is beneficial for cost reduction and cell performance since thinner absorber layers result in less bulk recombination.  Reducing the thickness of the absorber layer is especially advantageous to amorphous silicon solar cells since it has been shown to mitigate the Staebler-Wronski effect.

Template stripping is a technique that relies on the weak adhesion between coinage metals (Au, Ag, Cu) and SiO₂ (e.g. native oxide covered silicon) to provide ultrasmooth metal surfaces. We report on how template stripping can be extended to fabricate flexible, wafer scale, nanostructured metal surfaces which can be incorporated as the back reflector in various solar cell devices.  Furthermore, we show how template stripping is capable of producing photovoltaic back reflectors with complex, two dimensional, nanostructured gratings which result in improved device efficiency. Both theoretical and experimental results will be presented.