Time‐resolved spectroscopic studies on phenyl‐substituted poly(phenylenevinylene)s by picosecond excite‐ and probe technique

Abstract

Photoinduced picosecond absorption spectra of poly(1,4‐phenylene‐1,2‐diphenylvinylene) (DP‐PPV) and of related oligomeric and polymeric compounds were investigated in toluene solution. Between 400 and 900 nm the rise (5 … 40 ps) and decay (40 … 300 ps) of three transient absorption bands have been observed. The low energy absorption appears with a time delay of 5 ps and has its peak at 680 nm (1.8 eV). This band position is coincident with the well known ECS radical ion (polaron) absorption and is therefore assigned to this type of photogenerated charged species. The other two absorptions appear at higher energies. One of them is situated at 2.8 eV which is near to the band edge (2.9 eV). It originates immediately with the exciting pulse and is attributed to a neutral excited state. The other one (2.7 eV) is suggested to be due to an ECS diion (bipolaron).