Edge-Illuminated Ultrathin Crystalline Silicon Solar Cell

Abstract

This paper proposes a radically new solution to enhance the photoexcitation of silicon by directing the illumination onto the edge of the solar cell by means of fluorescence energy collection. This approach makes it possible to consider photovoltaic devices with efficiencies comparable to crystalline silicon thickness of only several micrometers. We will present the first theoretical results and discuss such structures where the path length of light is increased substantially, leading to efficient capture of the near bandgap photon flux. We shall show that using a realistic model for the fluorescent collector, overall device efficiency (collector + solar cell) of 13% maybe be achievable in the near future with a 1μm thick silicon structure. Efficiencies in excess of 17% can be reached with the application of photonics or using thicker silicon layers. We demonstrate that edge illuminated ultrathin silicon solar cells using fluorescent collectors can produce conversion efficiencies close to conventional c-Si solar cell but with greatly reduced material requirements.