Influence of Surface Modifier Molecular Structures on the Photovoltaic Performance of Sb₂S₃-Sensitized TiO₂ Nanorod Array Solar Cells

Herein, Sb₂S₃-sensitized TiO₂ nanorod arrays are prepared by the pyrolysis of 1.2 m antimony–thiourea complex solution in dimethylformamide (DMF) at 270 °C for 10 min. Various surface modifiers with different functional groups and carbon numbers of C₁₀H₂₁PO₃H₂, C₁₂H₂₅SO₃Na, C₃H₇COOH, C₅H₁₁COOH, C₇H₁₅COOH, C₁₁H₂₃COOH, C₁₃H₂₇COOH, C₁₅H₃₁COOH, and C₁₇H₃₅COOH are applied to modify Sb₂S₃-sensitized TiO₂ nanorod arrays. The corresponding solar cells are fabricated, and their photovoltaic performances are evaluated. To the different functional group surface modifiers, the improvement of functional group on photovoltaic performance is of the order of COOH > PO₃H₂> SO₃Na. To the different carbon number (4–18) surface modifiers, RCOOH with carbon number range of 8–12 exhibits better photovoltaic performance. Moreover, the Sb₂S₃-sensitized TiO₂ nanorod array solar cells with C₁₁H₂₃COOH achieve the best photoelectric conversion efficiency (PCE) of 5.37% with the open-circuit voltage (V_oc) of 0.53 V, short-circuit current density (J_sc) of 16.98 mA cm⁻², fill factor (FF) of 60.66%, and the average PCE of 5.11 ± 0.21% with the V_oc of 0.52 ± 0.01 V, J_sc of 16.65 ± 0.24 mA cm⁻², and FF of 58.93 ± 1.21%. The PCE of 5.37% corresponding to the use of spiro-OMeTAD as the hole-transporting material is a relatively high PCE for Sb₂S₃ solar cells.