Synthesis of hexagonal ZnO clubs with opposite faces of unequal dimensions for the photoanode of dye-sensitized solar cells.
Novel sub-micro sized hexagonal clubs of ZnO (HC-ZnO), which are coated as a scattering layer (SL) for the photoanode of a DSSC, are synthesized. X-ray diffraction (XRD) patterns of the ZnO clubs show clear peaks corresponding to wurtzite crystal phase of ZnO. Scanning electron microscopic (SEM) images show that each club has two opposite hexagonal faces (parts) of unequal dimensions. High resolution transmission electron microscopic (HR-TEM) image of a single ZnO club reveals that the ZnO is single crystalline and has wurtzite crystal structure; the image indicates a lattice spacing (d) of 0.26 nm; this is ascribed to the (002) planar spacing of the hexagonal ZnO. A solar-to-electricity conversion efficiency (η) of 3.36% is achieved for the cell with the double layer (DL) film, which is 16% higher than that of the cell with only transparent layer (TL) of commercial ZnO (2.89%) and far higher than that of the cell with SL (0.05%). The η of the cell with the DL (3.36%) could further be improved to 4.28% through the modification of the DL surface with TiO(x). Incident photo-to-current conversion efficiency (IPCE) curves, UV-vis absorption spectra, energy dispersive X-ray (EDX) spectra, and electrochemical impedance spectra (EIS) are also used to substantiate the results.
Department of Chemical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan.
Chuan-Pei
CP
Lee
Jen-Chieh
JC
Lin
Yi-Chun
YC
Wang
Chen-Yu
CY
Chou
Min-Hsin
MH
Yeh
R
R
Vittal
Kuo-Chuan
KC
Ho