Nano Lett. 11, 4812–4817 (2011)

Applying strain could provide a new way to enhance the performance of solar cells, according to a team of scientists at Georgia Tech in Atlanta, USA. Ya Yang and co-workers have shown that the open circuit voltage of solar cells made from ZnO nanowires and the organic semiconductor P3HT on a flexible polystyrene substrate increases under compressive strain. The mechanism for the enhancement is thought to be the piezotronic effect, whereby an applied strain modifies the energy bandgap of the solar cell's p–n junction through the creation of piezoelectric polarization charge. In their experiments, the researchers found that a compressive strain of −0.4% enhanced the open circuit voltage of the cell by nearly 30% from 0.2 V to 0.26 V, while the short circuit current remained almost constant. The researchers modelled the effect with Lippman theory to help understand and predict the phenomenon. They say these findings could be used to help optimize the performance of solar cells made from wurtzite structured materials.