Department of Chemical and Biological Engineering, Princeton University , A323 Engineering Quadrangle, Princeton, New Jersey 08544, United States.
J Am Chem Soc. 2014 Nov 5;136(44):15749-56. doi: 10.1021/ja5091035. Epub 2014 Oct 24.
Though both the crystal structure and molecular orientation of organic semiconductors are known to impact charge transport in thin-film devices, separately accessing different polymorphs and varying the out-of-plane molecular orientation is challenging, typically requiring stringent control over film deposition conditions, film thickness, and substrate chemistry. Here we demonstrate independent tuning of the crystalline polymorph and molecular orientation in thin films of contorted hexabenzocoronene, c-HBC, during post-deposition processing without the need to adjust deposition conditions. Three polymorphs are observed, two of which have not been previously reported. Using our ability to independently tune the crystal structure and out-of-plane molecular orientation in thin films of c-HBC, we have decoupled and evaluated the effects that molecular packing and orientation have on device performance in thin-film transistors (TFTs). In the case of TFTs comprising c-HBC, polymorphism and molecular orientation are equally important; independently changing either one affects the field-effect mobility by an order of magnitude.
尽管有机半导体的晶体结构和分子取向都已知会影响薄膜器件中的电荷输运，但单独访问不同的多晶型物并改变面外分子取向具有挑战性，通常需要严格控制薄膜沉积条件、薄膜厚度和衬底化学性质。在这里，我们展示了在不调整沉积条件的情况下，通过后沉积处理在扭曲的六苯并蔻烯（c-HBC）薄膜中独立调节晶体多晶型和分子取向。观察到三种多晶型物，其中两种以前没有报道过。利用我们在 c-HBC 薄膜中独立调节晶体结构和面外分子取向的能力，我们已经解耦并评估了分子堆积和取向对薄膜晶体管（TFT）中器件性能的影响。在包含 c-HBC 的 TFT 的情况下，多晶型物和分子取向同样重要；独立改变其中任何一个都会使场效应迁移率发生一个数量级的变化。
