Effect of alkaline sources on the characteristics and photovoltaic performance of vertical ZnO nanorods-based dye sensitized solar cells

Hexamethylenetetramine (HMT), urea (UR), sodium hydroxide (SH), and ammonium water (AW) were used as alkaline sources to prepare the one dimensional zinc oxide rods (ZORs) vertically on F-doped tin oxide (FTO) glass from a chemical bath deposition (CBD) method with zinc salt precursor. The morphology and optical properties of the prepared ZORs were characterized, and correlated to the power conversion efficiency (PCE) of the ZORs-based dye sensitized solar cells (DSCs). FESEM images indicate all the four alkaline sources produce the vertically-aligned one dimensional array ZnO structure and XRD results illustrate that prepared ZORs with significant wurtzite structure. ZORs from UR show the highest PL intensity, while SH the least one. The power conversion efficiencies of the ZORs-based DSCs are 0.56, 0.05, 0.70, and 0.02% for the alkaline sources of HMT, urea, SH, and AW, respectively. Electron lifetimes calculated from the electrochemical impedance spectroscopy (EIS) are 6.8, 1.8, 1.5, and 4.2 ms for SH, HMT, UR, and AW, respectively. Open circuit photovoltage decay (OCVD) measurement indicates similar changing trend of electron lifetime as that from EIS.