Photochemical hole burning of tetraphenylporphin in an aromatic polyimide

Abstract

Photochemical hole burning (PHB) was performed in free-base tetraphenylporphin (TPP) doped into an aromatic polyimide (PI). The microscopic ordered structure of PI, low energy excitation modes, and thermal stability of a hole burnt at 4.2 K were studied with the PHB measurements. Low energy excitation modes reflected microscopic ordered structure. Thermal stability of a hole showed little dependence on the ordered structure. It could be interpreted that the structural relaxation leading to the instability of a hole is a larger scale relaxation than the low energy excitation modes. This interpretation is consistent with the fact that the thermal energy for annealing temperature (30–80 K) is larger than the low energy excitation modes (∼ 10 cm −1).