Low temperature grown ZnO nanotubes for dye sensitized solar cells

Non-aligned and aligned ZnO nanotube (NTs) are synthesized by low temperature solution method are applied as photoanode materials for the fabrication of efficient dyesensitized solar cells (DSSCs). The crystalline and the morphological analysis reveals that the grown aligned ZnO NTs possesses a typical hexagonal crystal structure of outer and inner diameter ~250 nm and ~100 nm, respectively. ZnO seeding on FTO substrates is an essential step to achieve the aligned ZnO NTs. A DSSC fabricated with aligned ZnO NTs photoanode achieves high solar-to-electricity conversion efficiency of ~2.2% with short circuit current (JSC) of 5.5 mA/cm², open circuit voltage (VOC) of 0.65V and fill factor (FF) of 0.61. Significantly, the aligned ZnO NTs photoanode shows three times improved solar-to-electricity conversion efficiency than DSSC fabricated with nonaligned ZnO NTs. The enhanced performances are credited to the aligned morphology of ZnO NTs which executes the high charge collection and the transfer of electrons at the interfaces of ZnO NTs and electrolyte layer.