Efficient Energy Conversion - From Understanding to Application: Organic Photovoltaics and Solid State Lighting

Organic photovoltaics (OPVs) and solid-state white lighting are interesting and demanding areas of research as they both offer tremendous benefits to our environment and to our economy in these energy conscious times. OPVs use organic polymers or small organic molecules to absorb radiation from sunlight and convert the energy into electrical current. Made from earth abundant materials that can easily be solution processed at low temperatures, they provide a lost cost, flexible, renewable energy option that can provide power to all regions of the world, especially remote areas that cannot be easily connected to a power grid. Yet efficiencies and lifetimes of OPVs need to be improved before they can become a viable option for large-scale power generation. Solid-state white lighting, which uses a phosphor in conjunction with a blue or near-UV InGaN LED to produce white light, has many benefits over traditional incandescent and fluorescent lighting sources such as high efficiencies, low energy consumption, long lifetimes and a mercury-free design. One of the most efficient and widely used phosphors is the yellow emitting Y3Al5O12:Ce3+ (YAG:Ce), yet the origins of its high efficiency remain unknown. YAG:Ce is not the ideal phosphor though, it suffers from thermal quenching of luminescence at elevated temperatures and lacks strong representation in the red spectral region leading to a low color rendering. The phosphor research is therefore two-fold: to elucidate the origins of the high efficiency in YAG:Ce while using this understanding to strategically design new phosphors with optimal characteristics for solid state white lighting.