Computational study of the impact of regeneration and unwanted recombination reactions of Ru(II) phenanthroline compounds used as sensitizers in dyes sensitized solar cells

- Four carboxylated Ru(II) phenanthroline were modelled for application as sensitzers for DSSCs.
- The recombination and regeneration reactions of the dyes were computed.
- The effect of hyperfine, hyperpolarizabilities and the UV absorptions properties were examined.
- The band gap and interacting energy with I− can influence their efficiency.

The electronic, spectroscopic, regeneration and recombination reactions of four ruthenium(II) phenanthroline complexes with different number and position of the carboxylic acid group were modelled and compared to their reported experimentally obtained efficiencies as sensitizers for dye sensitizer solar cells (DSSCs). The results shows that the excitation of the compounds are associated with shorter CS bonds, lower band gap, and low self-spin electrons on the Ru ion. The interactions of the ruthenium complexes with I− ion indicated that this step is responsible for the electron transfer processes and regeneration while interaction with 2I− ion resulted in the separation of the two I− ion from the ruthenium compounds and their return to the ground states. Thermodynamic properties and the hyperfine values further confirm this observation. The results provided better insights on the regeneration and recombination reactions taken place in these compounds with respect to the discrepancies observed in their efficiencies as sensitizers for DSSCs. The results also show that the interacting energy of the Ru2+ with I− and their associated properties like hyperpolarizability and band gap play significant role in the reported experimental short-circuit photocurrent density (Jsc) and solar-energy conversion efficiency (η).

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