Dresden 2011 – scientific programme

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DS: Fachverband Dünne Schichten

DS 32: Spins in Organic Materials III (Focused Session, jointly with MA -- Organisers: Salvan, Hess, Timm)

DS 32.3: Talk

Wednesday, March 16, 2011, 17:30–17:45, GER 37

Light induced spin-interacting charge-transfer states in polymer:C60-fullerene blends — •Andreas Sperlich¹, Tom J. Savenije^1,3, Magdalena Zawadzki¹, Hannes Kraus¹, Carsten Deibel¹, and Vladimir Dyakonov^1,2 — ¹Experimental Physics VI, Julius-Maximilians-University of Würzburg, D-97074 Würzburg — ²ZAE Bayern, D-97074 Würzburg — ³Department of Chemical Engineering, Delft University of Technology, NL-2628 BL Delft, The Netherlands

Charge-transfer states (CTS) are widely considered to be an intermediate species between the primary photo-excited singlet exciton and the formation of separate electrons and holes in organic semiconductors and their blends. We demonstrate that these CTS, being interacting e-h pairs, can be studied using electron spin resonance (ESR).

At temperatures below 100K a spin-polarized pattern (E-A-E-A) of microwave emission (E) and absorption (A) can be detected. Several microseconds after the excitation pulse this polarization pattern transforms to a purely absorptive spectrum with two peaks (A-A). This spectrum is identical to the one obtained by cw ESR, which has previously been assigned to non-interacting positive and negative charges. For lower temperatures (<20K) additional features assigned to spin-interacting persistent e-h pairs were observed.