Nanostructured Devices for Third-Generation Photovoltaics
Abstract: Solar energy can serve as a virtually unlimited clean source of energy by converting sunlight into electrical power. Third generation photovoltaics based on surface nano-structuring of thin film solar cells presents a significant potential for the realization of high-efficiency, low-cost and mechanically flexible photovoltaic devices. Enhanced light absorption of single isolated nano-structures is due to a light-concentrating property of the subwavelength structures. In this case the absorption cross-section is significantly greater than the physical bounds of the subwavelength feature for a certain spectral range, and power conversion efficiencies (PCE) beyond the Shockley–Queisser limit were demonstrated. Various approaches to surface nano-structuring for photovoltaics were demonstrated to lead to absorption enhancement and to support tolerating short minority diffusion lengths for different photovoltaics materials.
At Max Planck Institute for the Science of Light we realize nano-structured thin-film solar cells using top-down low-cost fabrication techniques. In the seminar we will first review the opto-electrical behavior of a single isolated silicon nano-pillar coupled to a substrate. Secondly, the disparity between a single highly absorbing resonating cavity and light trapping in arrays composed of such structures will be presented, and design rules for array absorption optimization will be suggested. Finally, we will review a new light trapping paradigm for photovoltaics that bio-mimics the structure and arrangement of the photoreceptor cells in the fovea centralis region of the retina, and demonstrate the superiority of this concept against the most recent advancements in the field.