Synthetic Metals 159 (2009) 1298–1301 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Syntheses and properties of cyano and dicyanovinyl-substituted oligomers as organic semiconductors Erjing Wang a,c , Qing Meng a,c , Chengliang Wang a,c , Liqiang Li a,c , Hongxiang Li a,b,∗ , Wenping Hu a,∗∗ a Beijing National Laboratory for Molecular Sciences and Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China b Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China c Graduate School of Chinese Academy of Sciences, Beijing 100039, China article info Article history: Received 5 January 2009 Accepted 20 February 2009 Available online 27 March 2009 Keywords: Organic semiconductor Oligomer Electro-withdrawing group Transistor abstract Thiophene-phenylene co-oligomers with cyano and dicyanovinyl substituents at different positions were synthesized. Their stability and energy levels were estimated through thermal gravimetric analysis, UV–vis absorption spectra and electrochemistry. Interestingly, the absorption of BTCV covered the range of 430–610 nm, and thin film transistors of BTCV exhibited p-type behavior with high stability, suggesting BTCV a good candidate for solar cell. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Conjugated oligomers are one of the most important classes of organic semiconductor materials and have found wide appli- cations in organic field effect transistors (OFETs), solar cells, organic light emitting diodes (OLED) and so on [1]. As organic semiconductor materials, oligomers usually have good solu- bility and are facile to be modified, so that their property can be modulated easily to fit various applications. Electron- donating and electron-withdrawing groups are widely used to tune the energy level and property of oligomers. And the inter- molecular interactions and thin film morphology of oligomers sometimes changed dramatically when an electron-donating or electron-withdrawing substituent was introduced [2]. Moreover, the position of these substituents on oligomers could make dif- ferent effects on oligomer’s electronic properties [3]. So it is very important for material science to study the effect of electron- donating or electron-withdrawing substituents to the property of oligomers. Cyano and dicyanovinyl substitutents are common electron- withdrawing groups. Literatures reported organic semiconductors ∗ Corresponding author at: Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China. ∗∗ Corresponding author. E-mail addresses: lhx@iccas.ac.cn, lhx@mail.sioc.ac.cn (H. Li). with cyano groups at different position showed different elec- troluminescent behaviors in OLED and photophysical properties in solar cells [4]. Recently, it was reported the introduction of cyano groups could alter the molecular stacking and crystalline properties of oligomers [5]. Dicyanovinyl substituent –CH C(CN) 2 as strong electron-withdrawing group was often used in non- linear optical materials and OLEDs [6]. It was found that the introduction of dicyanovinyl substituent could enhance absorp- tion intensity and enlarge absorption range of oligomers, and thus improve the power conversion efficiency in solar cells [7]. Dicyanomethylene substituent, which has similar electron- withdrawing property to dicyanovinyl substituent, has been used as electron-withdrawing group to induce n-type behavior in OFET and mobility as high as 0.2 cm 2 V -1 s -1 was obtained [8]. Comparing with dicyanomethylene, dicyanovinyl substituent was comparatively easily synthesized. More important, unlike dicyanomethylene substituent, dicyanovinyl group did not alter the aromaticity of the linked rings, which would highly improve the environmental stability of the materials. From the above facets, it suggested that cyano and dicyanovinyl groups play versatile roles in modulating the material’s property. In order to further investigate the effect of these electron- withdrawing substituents to the property of oligomers, in this manuscript, phenylene-thiophenes co-oligomers containing dif- ferent number of –CN and –CH C(CN) 2 substituents on different position (Scheme 1) were synthesized and their properties were investigated. 0379-6779/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2009.02.032