Dresden 2014 – scientific programme

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DS: Fachverband Dünne Schichten

DS 29: Organic Electronics and Photovoltaics V (joint session with CPP, HL, O)

DS 29.8: Talk

Wednesday, April 2, 2014, 17:00–17:15, ZEU 260

High-Mobility, Low-Voltage Organic TFTs based on Air-Stable DNTT Derivatives: Time-Dependent Improvement in Contact Resistance and Dynamic Performance — •Ulrike Kraft^{1, 3}, Ute Zschieschang¹, Kazuo Takimiya², Edwin Weber³, and Hagen Klauk¹ — ¹Max Planck Institute for Solid State Research, Stuttgart, Germany — ²RIKEN Advanced Science Institute, Wako, Japan — ³Technical University Bergakademie Freiberg, Germany

The organic semiconductor dinaphtothienothiophene and its derivatives C10-DNTT and diphenyl-DNTT provide larger carrier mobilities and better air stability than, e.g., pentacene. We present a detailed comparison of the thin-film morphology, static and dynamic performance and stability of low-voltage (3 V) thin film transistors based on vacuum-deposited films. Freshly fabricated TFTs (channel length: 100 um) have hole mobilities ranging from 3 cm2/Vs (DNTT) to 5 cm2/Vs (diphenyl-DNTT), with on/off ratios of 10^7.

During the first few hours after fabrication, the effective mobility of short-channel TFTs (L=1 um) increases by about 20-30%, due to an improvement in the contact resistance (measured with TLM). The dependence of this effect on the exposure to different gas atmospheres, humidity and to light was investigated. To study the impact on the dynamic performance of the TFTs, we fabricated unipolar ring oscillators on flexible PEN substrates. The stage delay of DNTT TFTs (L=1 um) measured at 3 V drops from 920 to 410 ns during the first 4 days of exposure to ambient air, which is the shortest delay reported for flexible organic TFTs at supply voltages <10 V.