Fundamental study of the carrier transport in both the channel layer and the electrode-channel contact of organic semiconductor crystals is indispensable for achieving high-performance organic field-effect transistors. In this paper, we report the temperature-dependent carrier transport of high-mobility organic semiconductors called $2\text{–}\text{decyl}\text{–}7\text{-phenyl-}\left[1\right]\text{benzothieno}[3,2\text{–}b][1]\mathrm{benzothiophene}$ (Ph-BTBT-C10) and $3\text{-decyl-}9\text{-phenyl-}\left[1\right]\text{benzothieno}[3,2\text{–}b]\text{naphtho}[2,3\text{–}b]\text{thiophene}$ (Ph-BTNT-C10). The use of single-crystal films with controlled bilayer-number thickness enabled the simultaneous study of intralayer and interlayer transport at cryogenic temperatures. Four-probe measurement of two-bilayer- and three-bilayer-thick films of Ph-BTBT-C10 suggests that the access resistance is dominated by tunneling transport across the insulating alkyl-chain layers. Single-crystal thin-film transistors of these materials showed band-like carrier transport down to 80 K and the carrier mobility of Ph-BTBT-C10 reached $34\mathrm{c}{\mathrm{m}}^2/\mathrm{V}\mathrm{s}$. Detailed analysis of the low-temperature characteristics revealed small activation energy of approximately 5 meV and a sharp distribution of band tail states. These findings suggest that high crystallinity owing to the bilayer-type crystal structure effectively suppresses the localization of gate-induced carriers.

中文翻译：

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双层型有机半导体超薄单晶中的陷阱态抑制和带状传输

对有机半导体晶体的沟道层和电极-沟道接触两者中载流子传输的基础研究对于实现高性能有机场效应晶体管是必不可少的。在本文中，我们报告了称为迁移率的高迁移率有机半导体的温度依赖性载流子传输$2\text{–}\text{癸基}\text{–}7\text{-苯基-}\left[\mathrm{1个}\right]\text{苯并噻吩}[3，2\text{–}b][\mathrm{1个}]\mathrm{苯并噻吩}$ （Ph-BTBT-C10）和 $3\text{-癸基-}9\text{-苯基-}\left[\mathrm{1个}\right]\text{苯并噻吩}[3，2\text{–}b]\text{萘酚}[2，3\text{–}b]\text{噻吩}$（Ph-BTNT-C10）。使用具有受控的双层数厚度的单晶膜使得能够同时研究低温下的层内和层间传输。Ph-BTBT-C10的两层和三层厚膜的四探针测量表明，通过绝缘烷基链层上的隧道传输，访问电阻占主导地位。这些材料的单晶薄膜晶体管显示出低至80 K的带状载流子传输，Ph-BTBT-C10的载流子迁移率达到$34\mathrm{C}{\mathrm{米}}^2/\mathrm{V}\mathrm{s}$。对低温特性的详细分析显示，活化能很小，约为5 meV，并且带尾态分布很陡。这些发现表明，由于双层型晶体结构的高结晶度有效地抑制了栅诱导的载流子的定位。