Technical Proceedings of the 2014 Clean Technology Conference and Trade Show

Cleantech 2014

Chapter 2: Solar Power Technologies

S. Shepard, L. Patel, F. Rubaiat
Louisiana Tech University, US
103 - 105
solar energy, photovoltaics, light trapping, nanoparticle scattering
We consider the light-trapping enhancement of a silicon photovoltaic with conductive nanoparticles of various shapes, sizes and spacing as top-reflectors; used in conjunction with a periodic and a pseudo-random back-reflectors. The nanoparticles in the top-reflector are silver (with the appropriate Drude model) and the back-reflectors are perfect electric conductors. The power spectral density then multiplied by the responsivity of crystalline-Si and by the input spectral density (blackbody solar radiation herein, normalized to one) to form Jsc. We see that for a given top-reflector the choice of a periodic back-reflector can yield a higher Jsc for a crystalline-Si PV than the choice of a pseudo-random one. This (perhaps initially surprising) result: that a periodic structure can outperform a pseudo-randomly rough surface as a back-reflector is due to resonances that can be setup between it and the top-reflector. At a single (resonant) frequency it’s easy to see how this can happen. The surprise is that we can sometimes produce enough resonances (perhaps manifesting as a sufficiently broad one) to provide sufficient enhancement across the 700nm broad band of silicon’s responsivity to surpass Lambertian (although Lambertian probably is still optimal for the infinitely broadband case).
Periodic and Psuedo-Random Back-Reflector Nanoparticle Enhanced Light-Trapping in a Silicon Photovoltaic