Comparative Study of TiO 2 , ZnO, and Nb 2 O 5 Photoanodes for Nitro-Substituted Naphthoquinone Photosensitizer-Based Solar Cells.

This research focuses on the first demonstration of NO 2 Lw (2-hydroxy-3-nitronaphthalene-1,4-dione) as a photosensitizer and TiO 2 , ZnO, and Nb 2 O 5 as photoanode materials for dye-sensitized solar cells (DSSCs). The metal-free organic photosensitizer (i.e., nitro-group-substituted naphthoquinone, NO 2 Lw) was synthesized for this purpose. As a photoanode material, metal oxides, such as TiO 2 , ZnO, and Nb 2 O 5 , were selected. The synthesized NO 2 Lw contains an electron-withdrawing group (-NO 2 ) and anchoring groups (-OH) that exhibit absorption in the visible range. The UV-visible absorbance spectrum of NO 2 Lw demonstrates the absorption ascribed to ultraviolet and visible region charge transfer. The NO 2 Lw interacts with the TiO 2 , ZnO, and Nb 2 O 5 photoanode, as shown by bathochromic shifts in wavelengths in the photosensitizer-loaded TiO 2 , ZnO, and Nb 2 O 5 photoanodes. FT-IR analysis also studied the bonding interaction between NO 2 Lw and TiO 2 , ZnO, and Nb 2 O 5 photoanode material. The TiO 2 , ZnO, and Nb 2 O 5 photoanodes loaded with NO 2 Lw exhibit a shift in the wavenumber of the functional groups, indicating that these groups were involved in loading the NO 2 Lw photosensitizer. The amount of photosensitizer loading was calculated, showing that TiO 2 has higher loading than ZnO and Nb 2 O 5 photoanodes; this factor may constitute an increased J SC value of the TiO 2 photoanode. The device performance is compared using photocurrent-voltage ( J - V ) curves; electrochemical impedance spectroscopy (EIS) measurement examines the device's charge transport. The TiO 2 photoanode showed higher performance than the ZnO and Nb 2 O 5 photoanodes in terms of photoelectrochemical properties. When compared to ZnO and Nb 2 O 5 photoanodes-based DSSCs, the TiO 2 photoanode Bode plot shows a signature frequency peak corresponding to electron recombination rate toward the low-frequency region, showing that TiO 2 has a greater electron lifetime than ZnO and Nb 2 O 5 photoanodes based DSSCs.