Letizia Joseph A, Salata Michael R, Tribout Caitlin M, Facchetti Antonio, Ratner Mark A, Marks Tobin J
Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, USA.
J Am Chem Soc. 2008 Jul 30;130(30):9679-94. doi: 10.1021/ja710815a. Epub 2008 Jul 2.
Electron transporting (n-channel) polymer semiconductors for field-effect transistors are rare. In this investigation, the synthesis and characterization of new electron-depleted N-alkyl-2,2'-bithiophene-3,3'-dicarboximide-based pi-conjugated homopolymers and copolymers containing the 2,2'-bithiophene unit are reported. A novel design approach is employed using computational modeling to identify favorable monomer properties such as core planarity, solubilizing substituent tailorability, and appropriate electron affinity with gratifying results. Monomeric model compounds are synthesized to confirm these properties, and a crystal structure reveals a short 3.43 A pi-pi stacking distance with favorable solubilizing substituent orientations. A family of 10 homopolymers and bithiophene copolymers is then synthesized via Yamamoto and Stille polymerizations, respectively. Two of these polymers are processable in common organic solvents: the homopolymer poly(N-(2-octyldodecyl)-2,2'-bithiophene-3,3'-dicarboximide) (P1) exhibits n-channel FET activity, and the copolymer poly(N-(2-octyldodecyl)-2,2':5',2'':5'',2'''-quaterthiophene-3,3'-dicarboximide) (P2) exhibits air-stable p-channel FET operation. After annealing, P1 films exhibit a very high degree of crystallinity and an electron mobility > 0.01 cm (2) V(-1) s(-1) with a current on-off ratio of 10 (7), which is remarkably independent of film-deposition conditions. Extraordinarily, P1 films also exhibit terracing in AFM images with a step height matching the X-ray diffraction d spacing, a rare phenomenon for polymeric organic semiconductors. Another fascinating property of these materials is the air-stable p-channel FET performance of annealed P2 films, which exhibit a hole mobility of approximately 0.01 cm(2) V(-1) s(-1) and a current on-off ratio of 10(7).
用于场效应晶体管的电子传输（n沟道）聚合物半导体很少见。在本研究中，报道了新型贫电子的基于N-烷基-2,2'-联噻吩-3,3'-二羧酸二亚胺的π共轭均聚物以及含有2,2'-联噻吩单元的共聚物的合成与表征。采用了一种新颖的设计方法，利用计算模型来确定有利的单体性质，如核心平面性、可溶解取代基的可定制性以及合适的电子亲和力，结果令人满意。合成了单体模型化合物以证实这些性质，并且晶体结构显示出3.43 Å的短π-π堆积距离以及有利的可溶解取代基取向。然后分别通过山本聚合和斯蒂勒聚合合成了一个包含10种均聚物和联噻吩共聚物的系列。其中两种聚合物可在常见有机溶剂中加工：均聚物聚（N-（2-辛基十二烷基）-2,2'-联噻吩-3,3'-二羧酸二亚胺）（P1）表现出n沟道场效应晶体管活性，而共聚物聚（N-（2-辛基十二烷基）-2,2':5',2'':5'',2'''-四噻吩-3,3'-二羧酸二亚胺）（P2）表现出空气稳定的p沟道场效应晶体管操作。退火后，P1薄膜表现出非常高的结晶度，电子迁移率> 0.01 cm² V⁻¹ s⁻¹，电流开关比为10⁷，这与薄膜沉积条件显著无关。特别地，P1薄膜在原子力显微镜图像中还呈现出台阶状，台阶高度与X射线衍射d间距匹配，这对于聚合物有机半导体来说是一种罕见的现象。这些材料的另一个迷人特性是退火后的P2薄膜具有空气稳定的p沟道场效应晶体管性能，其空穴迁移率约为0.01 cm² V⁻¹ s⁻¹，电流开关比为10⁷。
