Ultrafast dynamics of the excitons in a series of axially and bridged substituted phthalocyanine thin films

Femtosecond degenerate pump–probe spectroscopy was carried out on thin films of a series of axially substituted phthalocyanines including tBu4PcInCl(tBu4 = tetra-(tert-butyl)), tBu4PcTiO, tBu4PcIn(p-TMP) [p-TMP = p-trifluoromethylphenyl], tBu4PcGa(p-CPO) [p-CPO = p-chlorophenoxy], and μ-oxo-bridged phthalocyanine dimers, e.g., [tBu4PcIn]2O, tBu4PcIn–O–GaPctBu4 and [tBu4PcGa]2O. We demonstrate that the long lived state of the dynamics is the triplet state and the behavior of the degenerate pump–probe was determined by exciton–exciton annihilation (E-EA), nonradiative recombination (NR) and intersystem crossing (ISC) processes. The E-EA process is via the long-range dipole–dipole interaction between excitons or motion-limited diffuse other than exciton hopping migrations. The dimers shows much efficient E-EA and the indium-contained samples have larger ISC rate than the others.