ZnO nanowires and structures that combine nanowires and nanoparticles were used as the wide band gap semiconducting photoelectrode in dye-sensitized solar cells (DSSCs). The nanowires provide a direct path from the point of photogeneration to the conducting substrate and offer alternative semiconductor network morphologies to those possible with sintered nanoparticles. Growing nanowires with dendrite-like branched structure greatly enhances their surface area, leading to improved light harvesting and overall efficiencies. Hybrid cells based on a combination of nanowires and nanoparticles can be tailored to take advantage of both the high surface area provided by the nanoparticles and the improved electron transport along a nanowire network. Solar cells made from branched nanowires showed photocurrents of 1.6 mA/cm2, internal quantum efficiencies of 70%, and overall efficiencies of 0.5%. Solar cells made from appropriate hybrid morphologies show photocurrents of 3 mA/cm2 and overall efficiencies of 1.1%, while both the nanowire and hybrid cells show larger open circuit voltages than nanoparticle cells.
Bibliographical noteFunding Information:
This work was supported by the University of California Energy Institute's Energy Science and Technology Program and made use of MRL Central Facilities supported by the MRSEC Program of the National Science Foundation under Award no. DMR00-80034. J.B.B. was supported by a National Science Foundation Graduate Fellowship. The authors would also like to thank Tom Jaramillo for assistance in absorbance and IPCE measurements.
- Dye-sensitized solar cells