Two n-type molecular materials are covalently combined into a new photovoltaic component for polymer solar cells. Light harvesting by the perylenediimide results in very fast energy transfer to the fullerene unit, as shown with femtosecond transient absorption spectroscopy in toluene solution. Two energy transfer rates are observed of 2.5 x 10(12) s(-1) (53%) and 2 x 10(11) s(-1) (47%), attributed to two conformations. The final excited state that is populated is a perylenediimide-based triplet state that is formed on the nanosecond time scale with a high yield.