High-efficiency photovoltaic energy conversion using surface acoustic waves in piezoelectric semiconductors

We present a theoretical proposal for a radically new design for photovoltaic energy conversion using surface acoustic waves (SAWs) in piezoelectric semiconductors. It involves generation of SAWs, which create a periodically modulated electric field in a pure (undoped) piezoelectric semiconductor. This electric field spatially separates photogenerated electrons and holes to the maxima and minima of SAW, thus preventing their recombinatio. The segregated electrons and holes are transported by the moving SAW with the speed of sound (about 300 km/s) to the collecting electrodes. Two types of electrodes collect electrons and holes, respectively, and produce dc electric output. This active design promises a very high rate of photovoltaic energy conversion. Recent experiments using SAWs, albeit designed for photon counting, not for photovoltaics, have demonstrated the quantum efficiency of the photon to current conversion of 70%.