Thiophene Thin-film Transistors Research Articles

Gate-bias and temperature dependence of charge transport in dinaphtho[2,3-b:2′,3′-d]thiophene thin-film transistors with MoO3/Au electrodes

We investigated the gate-bias and temperature dependence of the voltage–current (V–I) characteristics of dinaphtho[2,3-b:2′,3′-d]thiophene with MoO3/Au electrodes. The insertion of the MoO3 layer significantly improved the device performance. The temperature dependent V–I characteristics were evaluated and could be well fitted by the Schottky thermionic emission model with barrier height under forward- and reverse-biased regimes in the ranges of 33–57 and 49–73 meV, respectively. However, at a gate voltage of 0 V, at which a small activation energy was obtained, we needed to consider another conduction mechanism at the grain boundary. From the obtained results, we concluded that two possible conduction mechanisms governed the charge injection at the metal electrode–organic semiconductor interface: the Schottky thermionic emission model and the conduction model in the organic thin-film layer and grain boundary.

Low-Voltage Organic Transistors Based on Tetraceno[2,3-b]thiophene: Contact Resistance and Air Stability

The small-molecule organic semiconductor tetraceno[2,3-b]thiophene has been synthesized through an environmentally friendly synthetic route, utilizing NaBH4, rather than Al/HgCl2, for the reduction of the quinone. Low-voltage organic thin-film transistors (TFTs) have been fabricated using tetraceno[2,3-b]thiophene and, for comparison, pentacene and anthradithiophene as the semiconductor. The tetraceno[2,3-b]thiophene TFTs have an effective field-effect mobility as large as 0.55 cm2 V–1 s–1 and a subthreshold swing of 0.13 V/decade. In addition, it has been found that the contact resistance of the tetraceno[2,3-b]thiophene TFTs is substantially smaller than that of the anthradithiophene TFTs and similar to that of the pentacene TFTs. The long-term air stability of TFTs based on all three semiconductors has been monitored over a period of 12 months. The initial charge-carrier mobility of the tetraceno[2,3-b]thiophene TFTs is ∼50% smaller than that of the pentacene TFTs, but as a result of the greater ionization potential and better air stability induced by the terminal thiophene ring condensed at the thiophene-b-bond, the tetraceno[2,3-b]thiophene TFTs outperform the pentacene TFTs after continuous exposure to ambient air for just 3 months.