SEM imaging of acoustically stimulated charge transport in solids

Abstract

Applications of surface acoustic waves (SAWs) are of great interest for solar energy for the acoustically stimulated transport of charge carriers generated in semiconductors and dielectrics under the influence of light.1–4 A prospective application of SAWs in solar cells could provide a 90% increase in the cell efficiency. SAWs propagating in piezoelectric crystals (piezoelectric semiconductor GaN and GaAs crystals included) have opposite potential values in the SAW minima and maxima due to the piezoelectric effect. Electrons and holes generated by light in a semiconductor or in the subsurface layer of a piezoelectric crystal are correspondingly distributed between SAW minima and maxima. The charges are then transported by SAWs to the solar cell exit at the acoustic wave velocity. Taking advantage of the SAW presence in solar cells, the area of charge “harvest” from the surface of a semiconductor structure or a piezoelectric crystal can be increased, and correspondingly, the solar cell efficiency can be increased too.