Nanostructural control of ZnO photoelectrodes for enhancing solar energy conversion efficiency in dye-sensitised solar cells

Dye-sensitised solar cells (DSSCs) are one of the promising photovoltaic devices based on nanosized metal oxide semiconductors. We have focused on ZnO photoelectrodes and their nanostructural control in terms of nanomaterials processing. Since significant photophysical and electrochemical reactions take place around electrodes in the operation of DSSCs, their performance depends greatly on nanostructure of photoelectrodes. In thisreview article, we introduce our series of studies on nanostructural control of ZnO photoelectrodes to enhance the cell performance. It is shown that the introduction of macroporous ZnO particles as light scattering layers is effective to improve the light harvesting efficiency. Formation of silica nanolayers on ZnO electrodes is also proven to be beneficial to suppress the recombination of photogenerated electrons and enhance the charge collection efficiency. In both cases, short-circuit photocurrent density and open-circuit photovoltage were increased and hence, light-to-electricity conversion efficiency could be enhanced up to 4.80% only by controlling the photoelectrode structures.