Organic heteromultilayers:: electronic structure of sexithienyl/C60 thin films grown in ultra-high vacuum

Conjugated polymers have among the largest optical nonlinearities and interesting charge generation and transport properties. The combination of both these characteristics is appealing for optoelectronics. We report here on the spectroscopic characterization of alternated multilayers of T-6 and C-60 with the aim of understanding the electronic structure of a prototype donor-acceptor multilayer. We demonstrate the absence of a stable charge-transfer state at the interface. The strong photoluminescence reduction and a much faster radiative lifetime are indirect evidence of the formation of a metastable charge transfer. Deliberate doping of the fullerene layer with C-70 causes strong photoluminescence trapping into C-(70)-induced traps.