Aminonaphthoquinones as photosensitizers for mesoporous ZnO based dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) were fabricated on mesoporous ZnO using different novel 2R-(n-alkylamino)-1,4-naphthoquinone photosensitizers, viz; HA3; (2-propylamine-1,4-naphthoquinone), HA4; (2-butylamino-1,4-naphthoquinone), BrA3; (2-bromo-3-propylamino-1,4-naphthoquinone), BrA4; (2-bromo-3-butylamino-1,4-naphthoquinone). The crystallinity, morphology, optical, and electrochemical properties of the photosensitizers loaded ZnO were investigated by FE-SEM, UV-visible spectroscopy and J-V characteristics. Scanning electron micrograph (FE-SEM) indicates the surface morphologies of ZnO structures. A broad band of photosensitizers in UV region assigned to pi -> pi* transition while a visible region band assigned to n -> pi* charge transfer transition. Powder XRD pattern of mesoporous ZnO on fluorine-doped tin oxide (FTO) confirmed the presence of single-phase hexagonal wurtzite structure, without the impurity phase. DSSCs based on mesoporous ZnO electrodes were fabricated using these photosensitizers with an impressive power conversion efficiency of 0.12, 0.09, 0.13, and 0.20% obtained for HA3, HA4, BrA3 and BrA4 photosensitizers. The current-voltage measurements of DSSCs based on mesoporous ZnO showed an enhancement of open-circuit voltage (V-oc) from 0.29 to 0.33V. It confirms its active role photosensitizers for the energy barrier leading to a decrease in recombination losses. The unique mesoporous ZnO acts as the template for photogenerated charges and forms a barrier to reduce the recombination rate of the photoinjected electron-hole pairs at the electrode-electrolyte interface. (C) 2020 Elsevier B.V. All rights reserved.