Air-stable solution-processable unipolar n-type organic semiconductors are highly desired in the field of organic thin film transistors as n-type transistors are indispensable components in low-power-consumption complementary integrated circuits. The present work seeks to address this issue and describes the synthesis of two dicyano-substituted bis(2-oxoindolin-3-ylidene)benzodifurandione (BOIBDD) derivatives with engineered alkyl side chains for n-type transistors. Two kinds of side chains are used in this study: 2-hexyldecyl (C₁₆H₃₃) and 3-hexylundecyl (C₁₇H₃₅). Surprisingly, the small structural difference between side chains induced remarkable differences in the physical properties and electronic performance of the BOIBDD derivatives. In addition, cyano substitution into the backbone of BOIBDD derivatives was shown to be effective at lowering the HOMO and LUMO energy levels of BOIBDD derivatives to obtain unipolar n-type materials. Compared with fluorine substitution, cyano substitution was readily realized by a simple and straightforward reaction using cheap CuCN as a cyanation reagent. Both atomic force microscopy (AFM) and X-ray diffraction (XRD) studies have confirmed that the BOIBDD derivative with 3-hexylundecyl side chains tended to form highly crystalline structures in the solid state. More interestingly, thermal annealing of this compound at a temperature as low as 75 °C, well below its melting point of 305 °C, can still further improve its crystallinity and thus significantly increase its electron mobility by 43 times to 0.1 cm² V^–1 s^–1 in air. The insight gained from this study will shed some light on the design of new air-stable high-performance n-type organic semiconductors.

中文翻译：

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3,7-双（2-氧代吲哚-3-亚基）苯并[1,2- b：4,5 - b ']二呋喃-2,6-二酮二氰化物，带有工程化侧链，用于单极n型晶体管

在有机薄膜晶体管领域中，由于在低功耗互补集成电路中不可缺少的组件是n型晶体管，因此对有机薄膜晶体管领域中的空气稳定溶液可处理的单极性n型有机半导体提出了很高的要求。本工作试图解决该问题，并描述了用于n型晶体管的两个具有工程烷基侧链的二氰基取代的双（2-氧代吲哚-3-亚基）苯并二呋喃二酮（BOIBDD）衍生物的合成。本研究中使用了两种侧链：2-己基癸基（C ₁₆ H ₃₃）和3-己基十一烷基（C ₁₇ H ₃₅）。令人惊讶的是，侧链之间的小结构差异引起了BOIBDD衍生物的物理性质和电子性能的显着差异。另外，氰基取代到BOIBDD衍生物的骨架中被证明可有效降低BOIBDD衍生物的HOMO和LUMO能级以获得单极性n型材料。与氟取代相比，使用廉价的CuCN作为氰化试剂，可以通过简单直接的反应容易地实现氰基取代。原子力显微镜（AFM）和X射线衍射（XRD）研究都证实具有3-己基十一烷基侧链的BOIBDD衍生物倾向于在固态下形成高度结晶的结构。更有趣的是，该化合物在低至75°C的温度下进行热退火，空气中² V ^–1 s ^–1。从这项研究中获得的见识将为新型空气稳定的高性能n型有机半导体的设计提供一些启示。