Berlin 2005 – scientific programme

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SYOO: Organic Optoelectronics and Photonics

SYOO 6: Poster

SYOO 6.53: Poster

Monday, March 7, 2005, 18:00–20:00, Poster TU A

Trap Limited Hole Mobility in Semiconducting Poly(3-hexylthiophene) — •Vladimir Dyakonov^1,2 and Zivayi Chiguvare¹ — ¹Energy and Semiconductor Research, University of Oldenburg, D-26111 Oldenburg, Germany — ²Experimental Physics, University of Würzburg, Am Hubland, 97074 Wüzburg, Germany

Bulk transport properties of poly(3-hexylthiophene) (P3HT) were studied by analyzing temperature dependent current-voltage characteristics of the polymer thin films sandwiched between Indium Tin Oxide/polystyrene sulfonate doped Polyethylene dioxy-thiophene (ITO/PEDOT)and aluminium electrodes. It was found that the contacts limit charge injection under reverse bias, but under forward bias the current is limited by space charge that accumulates near the hole injecting electrode (ITO/PEDOT) resulting in a rectification of 10⁵. The forward current density obeys a power law of the form J ∼ V^m, with m>2, described by space charge limited current in the presence of exponentially distributed traps within the band gap. In this work we describe the deduction, and discuss the limits, of an expression for the calculation of the total trap density, based on the exponential trap distribution model, which yielded reasonable agreement with our experimental J(V) data. The total deep hole trap density was estimated to be 3.5 × 10¹⁶ cm⁻³, and the activation energy extrapolated to zero Kelvin was obtained to be 0.054 eV. Temperature dependent hole mobility in P3HT under trap-free space charge conditionswas also estimated.