Near-field optical beam-induced currents in CdTe/CdS solar cells: Direct measurement of enhanced photoresponse at grain boundaries

Using near-field optical beam induced current, we spatially resolve the photocurrent in polycrystalline CdTe/CdS solar cells, and observe increased photocurrent collection at grain boundaries (relative to the intragrain volume). This observation supports previously reported hypotheses that grain boundaries present a hole-barrier, thereby assisting in charge separation at the grain boundaries in these devices. The results offer compelling evidence, in an actual working-device structure, of the role of grain boundaries in explaining the surprisingly high performance of these highly defected devices. (C) 2004 American Institute of Physics.