Recent advances in nanophotonic light-trapping technologies offer promising solutions in developing high-efficiency thin-film solar cells. However, the cost-effective scalable manufacturing of those rationally designed nanophotonic structures remains a critical challenge. In contrast, diatoms, the most common type of phytoplankton found in nature, may offer a very attractive solution. Diatoms exhibit high solar energy harvesting efficiency due to their frustules (i.e., hard porous cell wall made of silica) possessing remarkable hierarchical micro-/nano-scaled features optimized for the photosynthetic process through millions of years of evolution. Here we report numerical and experimental studies to investigate the light-trapping characteristic of diatom frustule. Rigorous coupled wave analysis (RCWA) and finite-difference time-domain (FDTD) methods are employed to investigate the light-trapping characteristics of the diatom frustules. In simulation, placing the diatom frustules on the surface of the light-absorption materials is found to strongly enhance the optical absorption over the visible spectrum. The absorption spectra are also measured experimentally and the results are in good agreement with numerical simulations.

Recent designs in nanophotonic light-trapping technologies offer promising potential to develop high-efficiency thin-film solar cell at dramatically reduced cost. However, the lack of a cost effective scalable nanomanufacturing technique remains the main road-block. In nature, diatoms exhibit high solar energy harvesting efficiency due to their frustules (i.e., hard porous cell wall made of silica) possessing remarkable hierarchical nano-features optimized for the photosynthetic process through millions of years evolution. To explore this unique light trapping effect, different species of diatoms (Coscinodiscus sp. and Coscinodiscus wailesii) are cultured and characterized by Scanning electron microscope (SEM). Rigorous Coupled Wave Analysis (RCWA) and Finite-difference time-domain (FDTD) method are employed to numerically study the nanophotonic light-trapping effect. The absorption efficiency is significantly enhanced over the spectrum region centered on 450nm and 700nm where the electric fields are found strongly confined within the active layer. The transmission and reflection spectra are also measured by optical spectroscopy and the experimental results are in good agreement with numerical simulations.