Effect of diphenylamine substituent on charge-transfer absorption features of the iridium complexes and application in dye-sensitized solar cell

• Diphenylamine modified IrIIIbis(phenylpyridinato)-4-carboxylpicolinate was synthesized.
• Diphenylamine influenced absorption energy and orbital electron density distribution.
• Conversion efficiency of 2.51% and open circuit voltage of 0.68 V was achieved.

The new complex IrIIIbis(4-diphenylaminophenylpyridinato)-4-carboxylpicolinate (complex 3) tailored by electron-donating diphenylamine (DPA) was synthesized and characterized for dye-sensitized solar cells (DSSCs) application. The introduction of the DPA moiety to phenylpyridine ligand makes the absorption bands of the complex 3 extend to 650 nm, and adjusts the highest occupied molecule orbital to be mainly localized on DPA-ppy (diphenylaminophenylpyridine) ligands (accounting for 74.44% for one DPA-ppy ligand) while the lowest unoccupied molecule orbital to be lied on the pic (pyridine-2,4-dicarboxyl acid) moiety (96.80%). TD-DFT calculation further shows the charge-transfer transitions from ligand DPA-ppy and Ir atom to the pic anchoring moiety principally contribute to the absorption bands of the complex 3 in the visible region, which is well beneficial to electron injecting into TiO2 film. For DSSCs using complex 3 as sensitizer, the energy conversion efficiency is up to 2.51%, with a short circuit current density of 7.51 mA/cm2 and an open circuit voltage of 0.68 V. These results indicate that it is possible for IrIII complex to achieve more efficient cell parameters if more rational IrIII complexes are developed.

The diphenylamine was introduced to IrIIIbis(phenylpyridinato)-4-carboxylpicolinate to improve light-harvesting capacity of the resulting complex and induce favorable orbital electron density distribution for electron-injecting into TiO2 film when used as photosensitizer of dye-sensitized solar cells. As a result, a 2.51% conversion efficiency and 0.68 V open circuit voltage was achieved.Figure optionsDownload as PowerPoint slide