Constructing ZnO nanorod array photoelectrodes for highly efficient quantum dot sensitized solar cells

Abstract

This work reports on a ZnO nanorod (NR) array photoelectrode for CdS/CdSe quantum dot cosensitized solar cells (QDSCs), which generated a high power conversion efficiency of 3.14%. ZnO NR arrays were fabricated by growing on a seeded indium-doped tin oxide (ITO) substrate without using a template or high temperature conditions. The ZnO NR served as the backbone for direct electron transport in view of its single crystallinity and high electron mobility. To improve the performance of the QDSC, we introduced a facile chemical surface modification of the ZnO NR array photoelectrodes. The chemical processing not only formed a barrier layer of TiO₂ nanoparticles on the surface of the ZnO NR, which suppresses charge recombination by preventing the electrons in the ZnO conduction band from transferring to the oxidized ions in the electrolyte, but also modified the surface characteristics of the ZnO NR so as to harvest a greater amount of QDs and increase the short current density of the QDSC. As a result, the QDSC assembled with the modified ZnO NR array photoelectrode exhibited a high performance with J_sc, V_oc, FF and η performance values equal to 9.93 mA cm⁻², 0.61 V, 0.52 and 3.14%, respectively.