Preparation And Photoelectrochemical Properties Research Of ZnO/Cu₂O Sensitized Solar Cells

Dye-sensitized solar cells （DSSC） are considered to be a promising alternative toconventional solar cells due to its high conversion efficiency and low cost.Well-aligned ZnO nanorod arrays can effectively reduce the grain boundary barrierand the transmission loss in electronic transmission which have been regaerd as oneof the greatest potential photoanode material. However, ZnO can only absorb theultraviolet portion of the light due to its large band gap. In order to broaden thespectral absorption range, it typically needs compound with narrow band gapsemiconductor such as Cu₂O and CdS. The main contents and obtained results aresummarized as follows:1.Well-aligned ZnO nanorod arrays were grown from ZnO nanocrystal seeds onFTO （F:SnO₂） substrates. The infuence of solution concentration, spin coating timesand annealing temperature of seed-layer on the density of ZnO nanorod arrays wereinvestigated. It could be observed that diameter of rods got small and nonuniformwith the reduction of concentration. The density of ZnO nanorod arrays reduced as theannealing temperature increased because of the interaction among the particles whichled the grains to merge together to form bigger ZnO seed islands. It could beconcluded that repeating the spin coating process could greatly improve thedispersibility of ZnO seeds on the substrate, and the density of ZnO nanorod arrayswas increased.2.Cu₂O nanocrystalline were deposited by chemical bath deposition （CBD） methodon the above ZnO nanorod arrays substrates. The microscopic structure andphotoelectric performance of the ZnO/Cu₂O composite films were investigated. ThenDSSC were assembled with ZnO/Cu₂O photoanodes and their photoelectrochemicalbehavior were investigated. The results were as follows: the absorbance of theZnO/Cu₂O composite film was extended to the visible region and the composite filmshowed well-defined current rectifying behavior; the photoelectric efficiency can beenhanced by increasing annealing temperature or spin coating times of ZnOseed-layer which could improve crystallinity of ZnO nanorod arrays or capture morephotons. The best photoelectric conversion efficiency of the DSSC reached about0.1%with open-circuit voltage of0.27V and short-circuit current density of0.1mA/cm².3.The CdS quantum dots （QDs） were prepared by a simple ultrasound-assistedCBD process and were inserted between ZnO and Cu₂O. The effect of deposition time （1,3,5,7min） of CdS layer on the photoelectrochemical performance of DSSC withZnO/CdS/Cu₂O composite photoanodes was investigated. The results showed thatshort-circuit current increased significantly and photoelectric efficiency could beenhanced by incereasing the deposition time of CdS. When the time increased further,photoelectric efficiency began to decline, which may be caused by poorcharge-injection efficiency. The best cell photoelectric efficiency was0.31%bydeositing CdS for5min.