CdS sensitized vertically aligned single crystal TiO₂ nanorods on transparent conducting glass with improved solar cell efficiency and stability using ZnS passivation layer

Photoanodes consisting of CdS sensitized titania nanorods with ZnS passivation layer are applied for solar cells. Single crystal TiO₂ nanorods have been directly grown vertically on transparent conducting glass by a facile hydrothermal method and deposited with CdS and then a ZnS layer on the TiO₂ surface via a successive ionic layer adsorption and reaction (SILAR) method. The properties of ZnS/CdS/TiNR are characterized by XRD, SEM, TEM, UV-Vis, XPS, and electrochemical analysis. The effect of ZnS amount is studied in this system. Electrochemical results indicate the photocurrent density (J_sc) is greatly improved by increasing amount of ZnS. The incident photo-to-current conversion efficiency (IPCE), open-circuit voltage-decay (OCVD) method, and electrochemical impedance spectra (EIS) obviously substantiate these results. By optimizing the length of titania nanorods and the amount of CdS and ZnS, the best efficiency of 1.8% was achieved for solar cell under AM 1.5 G illumination with J_sc = 4.19 mA cm^-2, V_oc = 0.82 V and FF = 54%.