Pentacene hole field-effect mobility

Fig. 2 The evolution of the hole field-effect mobility of various organic semiconductors in time. The data of Table 1 are grouped into families of molecules with similar main chain. Additionally, hole field-effect mobilities of rubrene and pentacene in single crystals are depicted. For comparison, the electron mobilities of a-Si H and poly-Si are shown...

A pentacene OFET where a Si02 gate dielectric has been implemented, shows typically decent p-channel behavior with field-effect mobilities exceeding 0.1cm V [60] while a lack of any electron conduction is usually observed. This disparity in the n- and p-type behavior is also mirrored in Fig. 8 where exem-plarily the evalution of the electron and hole field-effect mobilities of pentacene over the last 15 years is depicted. Respective data are listed in Table 2. While from the year 1992 up to now the hole field-effect mobility in pentacene steadily increased from 0.002 to 5cm V s the first signature of electron transport in field-effect transistors was not found before 2003 [35]. Nowadays, comparable field-effect mobilities for electrons and holes are obtained in transistors comprising polycrystalline pentacene [60, 61]. 

Fig. 8 The evolution of the electron and hole field-effect mobility of pentacene in time. For comparison, the electron mobility of a-Si H is shown. The data are listed in Table 2...

Fig. 16 Electron and hole field-effect mobilities of pentacene-based OEETs for different polymeric gate dielectrics depicted in Fig. 15. The respective mobilities have been extracted from transfer characteristics of either unipolar p-channel or unipolar n-channel transistors. For one gate dielectric gold or Ca source/drain metals have been used to define the polarity of the field-effect transistors...

Benson et al. on the other hand achieved electron transport in pentacene based OFETs by employing hydroxyl-free polymeric gate dielectrics [61]. For example, polymethylethacrylate (PMMA), polycarbonate (PC) and polystyrol (PS) allowed for a pronounced electron and hole conduction in the transistor channel. The chemical structure of the used polymers and the schematic device setup are depicted in Fig. 15. The field-effect mobilities obtained are plotted in Fig. 16. The results prove that the charge carrier transport properties of both charge carrier species are rather... 

Pentacene routinely yields field-effect transistor (FET) devices with reliable hole mobility of 1 cm2 V-1 s 1 [6], with mobility > 3 cm2 V-1 s-1 reported for thin-film devices on polymer gate dielectrics [9]. For transistors fabricated on single crystals of pentacene, the measured mobility approaches 60 cm2 V-1 s 1 [10]. 

Watanabe et al. also constructed field effect transistors from hexacene single crystals [32]. The authors report an averaged (14 devices) mobility of 0.88 cm s with a threshold at 34 V and an on/off ratio of 10" -10. The best hole mobility observed was 4.28 cm s. The conductivity of crystalline hexacene (2.21 x 10 S m ) was slightly higher than that of pentacene [32]. The hole mobilities of hexacene thin films have been measured very recently [34]. 

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