Photon management in nanostructured solar cells

The unique geometry and intriguing physical properties of nanostructure-based solar cells gives them great potential to achieve the goals of cost-effectiveness and high-efficiency. With nanostructured solar cells it is expected to be possible to break the Shockley-Queisser limit. This potential has driven widespread research and development in photon management to enhance light absorption over the past decade. However, efficiency is not proportional to light absorption. Nowadays, researchers are starting to address this issue. A thorough understanding of the advantages and the scope of the application of each photon management scheme is critical to finding a breakthrough for this predicament. In this review, we present the theorems and describe recent progresses in primary photon management schemes for nanostructures, including antireflection, light scattering, and resonance (e.g., metallic resonance, dielectric resonance, and photonic crystals). The antireflection effect allows more light to enter the solar cell. Light scattering enhances the interaction between the light and the nanostructure, extending the light propagation paths in the devices. Resonance effects can redirect and precisely confine the light to the region where efficient photoelectric conversion efficiency occurs. Finally, we discuss the challenges of nanostructured solar cells, and indicate potential routes to overcome the performance-limiting problems.