Band-engineered semiconductors and phosphor materials for efficient solid-state lighting

Band-engineered semiconductors and phosphor materials for efficient solid-state lighting contributes toward the development of sustainable lighting technology for the 21st century. Lighting consumes ~1 TW of power worldwide, with greenhouse gas emission equivalent to 70% of the world's car emission. Solid-state lighting using semiconductor light emitting diodes (LEDs) has been widely recognized as the next generation energy-efficient lighting technology, since LEDs feature superior efficiency, longer lifetime, and lower environmental hazard when compared with conventional lighting sources. Currently a blue LED is usually combined with phosphor coating to generate white light. There are two major challenges to this technology: (1) LED Efficiency droop at high current density required for lighting; (2) Optical energy losses due to converting blue photons to lower energy photons by phosphors. To attack the former issue we are exploring band-engineering of semiconductors near direct-indirect gap transition to achieve anti-droop properties. For the latter issue we are investigating more efficient phosphor materials especially in the yellow-red regime to enhance its conversion efficiency. We are also conducting research on long-afterglow phosphors which can store optical energy during the day and emit light at night for emergency lighting and decorative lighting.

Faculty contact: Jifeng Liu