Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 36: Poster III

HL 36.6: Poster

Wednesday, February 27, 2008, 16:30–19:00, Poster D

Electron spin resonance studies of sol–gel-processed anatase-TiO₂-nanocrystals and charge transfer in blends with P3HT — •Andreas Sperlich¹, Jan Friedman^1,2, Ingo Riedel^1,2, Carsten Deibel¹, and Vladimir Dyakonov^1,2 — ¹Experimental Physics VI, Physical Institute, Julius-Maximilians-University of Würzburg, Am Hubland, D-97074 Würzburg — ²ZAE Bayern, Div. Functional Materials for Energy Technology, Am Hubland, D-97074 Würzburg

Light-induced electron spin resonance (L)ESR studies of photogenerated charge carriers in mesoporous films of TiO₂ blended with poly(3-hexylthiophene) (P3HT) were performed. The TiO₂-films were produced by sol-gel processes. XRD–measurements confirm anatase-structure. In pure films of TiO₂, several distinct lines are observed under illumination. These excitated states are known as “photodoping” and lead to enhanced electrical conductivity. With ESR, they can be assigned to Ti₃⁺ and O₂⁻ crystal and surface states which form paramagnetic electron and hole traps. Blended with P3HT the spectrum is dominated by one symmetrical line that originates from polarons on the polymer backbone. With different illumination conditions (UV vs. white light) it can be shown that both, electron transfer from the polymer to the TiO₂ and hole transfer in the other direction, are possible processes for the generation of free charge carriers. The charge transfer efficiency is important for applications in organic–inorganic hybrid solar cells.