Ultrafast excited state dynamics of iridium(iii) complexes and their changes upon immobilisation onto titanium dioxide layers

Abstract

Time-resolved spectroscopy was applied to investigate the excited state dynamics of two heteroleptic Ir(III) complexes with the general formula [Ir(C^N)₂(N^N)]⁺, where C^N and N^N represent different cyclometalating and diimine ligands, respectively. The excited state relaxation is influenced by the ligand substitution as well as the light polarisation. Vibrational relaxation occurs in the sub-ps timescale and interligand charge transfer results in polarisation dependent signal dynamics with a time constant of about 30 ps. Electron injection from the iridium dye to TiO₂ is analysed with respect to potential applications in solar energy conversion.