"Fueling Human Progress with Sunlight"
The recent rapid drop of solar module prices and global growth of photovoltaics has moved the scientific research frontiers for solar energy conversion towards new opportunities including i) increasing the energy harvest of silicon photovoltaics, ii) widely deployable ultrahigh efficiency (η = 30-50%) photovoltaics and iii) direct synthesis of energy-dense chemical fuels from solar energy, including hydrogen and products from reduction of carbon dioxide. I will illustrate several examples of how photonic design combined with material synthesis advances can enable progress in each of these areas. Photonic design approaches such as effectively transparent contact design and bifacial module illumination can increase both the power and efficiency obtained from silicon modules. Highly luminescent semiconductors have opened new directions for ultrahigh efficiency photovoltaics, but these must also compete on cost; I will describe a luminescent solar concentrator flat panel module that enables 30-100x concentration of diffuse sunlight onto small III-V compound semiconductor cells. Semiconductors coupled to water oxidation and reduction catalysts have enabled approaches to stable, >10% efficiency solar-to-hydrogen generation using artificial photosynthetic structures. I will report on challenges for >15% solar-to-hydrogen efficiency devices and outlook for >20% STH. Present work and future directions in electrocatalytic and photocatalytic materials for artificial photosynthesis aimed at catalytic reduction of carbon dioxide will also be discussed.