Enhancement of Photovoltaic Properties of Ti-modified Nanocrystalline ZnO Electrode for Dye-sensitized Solar Cell

摘要

Nano-porous semiconducting materials have been an intensive research field for many photovoltaic (PV) applications.The Gratzel-type dye-sensitized solar cell (DSSC) is one of the important devices of those applications.Using TiO_2 nanocrystalline electrode,it achieved recently the best energy conversion efficiency (eta) as high as 11%.ZnO has similar electronic properties with TiO_2 including conduction band (CB) position and band gap,so it has been also regarded as a good candidate for DSSC.Moreover,various simple and effective synthetic routes have been developed for nanocrystalline ZnO materials,while the optimized nanocrystalline TiO_2 colloid can be prepared only through the hydrothermal method until now.Nevertheless,ZnO-based DSSCs showed PV properties much inferior to TiO_2-based devices,though some systems using big particles exhibit slightly improved properties.For instance,Fitzmaurice et al.showed that 0.8 mum-thick ZnO electrode composed of 15 run ZnO particles exhibited a low eta of 0.4% at AM 1.5 illumination with about one sun light intensity of 119 mW/ cm~2 with small IPCE (incident photon-to-current conversion efficiency) value of 13% at 520 nm.