Luminescent solar cell that emits light achieves record efficiency

While the concept seems fundamentally counterintuitive, researchers at the University of California–Berkeley (UC Berkeley) have suggested and demonstrated that a highly efficient solar photovoltaic (PV) cell is also an efficient emitter of photons. A luminescent solar cell prototype developed by Alta Devices (Santa Clara, CA), the company that is commercializing the technology, achieved a 28.8% optical-to-electrical conversion efficiency—record performance for a single-junction PV cell and fast approaching the 33.5% theoretical Shockley-Queisser efficiency limit.

Based on the thermodynamic link between absorption and emission, a solar cell that easily emits photons also produces a higher voltage. When absorbed sunlight in the gallium-arsenide structure produces electrons and holes, these carriers have no place to go at the open-circuit condition. The carrier-density buildup causes external fluorescence that balances the incoming sunlight. An external fluorescence improvement from high carrier density also occurs in the best light-emitting diode (LED) devices. High carrier density produces high voltage and likewise, improved optical-to-electronic conversion efficiency. That is, the best solar cells behave just like ideal LEDs, with very low nonradiative losses and internal luminescence efficiency values much greater than 90%. Contact Owen Miller at [email protected].