Electrodeposition of zinc oxide on transparent conducting metal oxide nanofibers and its performance in dye sensitized solar cells

Abstract

Transparent conducting nanofibers of indium tin oxide (ITO) and antimony tin oxide were prepared on fluorine doped tin oxide glass substrates by electrospinning. Onto the obtained nanofiber mats first a dense zinc oxide layer followed by a nanoporous ZnO layer were electrochemically deposited. Transmission electron microscopy shows that only ITO nanofibers were covered with dense ZnO layers. For application in dye-sensitized solar cells (DSSCs) the dense layer is needed in order to suppress the back reaction of photogenerated electrons from the ZnO to the electrolyte. Therefore only films with ITO nanofibers were tested as porous electron collection layers in DSSC in view of electron transport and electron collection efficiency, and compared to ZnO layers electrodeposited under identical conditions but without nanofibers. Contrary to the expectation the conductive nanofibers do not improve the electron transport in the photoelectrodes and the solar to electrical conversion efficiency is limited to about 2.4%. It is discussed why the presence of nanofibers mats, which was found to be advantageous for TiO2-based DSSCs before, is not favorable for ZnO-based DSSCs.