Credit: © 2009 AIP

Exploiting the physical properties of semiconducting quantum dots and nanowires offers a new approach to improving the power conversion of conventional solar cells made from two-dimensional thin films. Eray Aydil and colleagues at the University of Minnesota have now demonstrated a threefold increase in power conversion efficiency of solar cells made from zinc oxide (ZnO) nanowires infiltrated with lead selenide (PbSe) quantum dots compared with conventional cells based on PbSe quantum dots and ZnO thin films1.

The hybrid nanowire–quantum-dot solar cells were produced by first sputtering a thin layer of ZnO on an optically transparent indium-tin-oxide electrode, and producing ZnO nanowires by wet chemistry. PbSe quantum dots were then infiltrated into the ZnO nanowires by repeated dipping into a colloid of ∼2.1-nm-diameter PbSe quantum dots.

The efficiency of the solar cells made using ZnO nanowires was found to be three times greater than thin film ZnO devices made with the same amount of quantum dots. These results can be explained in terms of higher exciton and charge collection efficiency of the hybrid structures. The power efficiency could be further improved by using greater densities of quantum dots and longer ZnO nanowires.