C8 BTBT薄膜结晶形貌及OTFT器件性能研究

以p型共轭有机小分子2,7二辛基1]苯并噻吩并3,2‐b]苯并噻吩(C8‐BTBT)作为底栅顶接触有机薄膜晶体管(OTFT)的有源层,采用浸渍提拉法、喷墨打印法和真空蒸镀法三种制备工艺,探究半导体薄膜载流子迁移率与结晶形貌的关系,发现不同工艺下有机小分子呈现出不同的生长行为和结晶情况,在很大程度上决定了OTFT器件性能的优劣;此外,通过XRD分析研究了退火处理对C8‐BTBT结晶的影响。结果表明,真空蒸镀制备的薄膜具有更高的结晶度、衬底覆盖率高,并且呈现出SK(Stranski‐Krastanov)模式的结晶生长特征,相应器件中陷阱密度最低,迁移率高达5.44 cm^2·V^-1·s^-1,开关比超过106;且退火处理会严重破坏C8‐BTBT薄膜的结晶。因此,控制半导体层的生长行为,提升半导体层的覆盖率和结晶度是制备高性能共轭小分子OTFT器件的有效途径。

Study of Crystallographic Morphology and OTFT Properties of C8 BTBT Thin Films

In order to investigate the relationship between carrier mobility and crystal morphology of semiconductor thin films,the p-type conjugated organic small molecule 2,7 dioctyl1]benzothieno3,2-b]1]benzothiophene(C8-BTBT)was adopted as the active layer of bottom-gate top-contact organic thin film transistor(OTFT),three kinds of processes,and dip-coating,ink-jet printing and vacuum evaporation,were used to prepare the C8-BTBT film.The growth behavior and crystalliza‐tion of small organic molecules and their effects on the properties of OTFT devices varied with different processes.In addition,the effect of annealing treatment on crystallization of C8-BTBT was studied by XRD measurements.The results show that the films deposited by evaporation have higher crystallinity,high substrate coverage,and exhibit the Stranski-Krastanov(SK)growth mode,and the trap density of the corresponding device is the lowest,so that the mobility is as high as 5.44 cm^2·V^-1·s^-1 and the on/off is more than 106.In addition,annealing could severely destroy the crystallization of C8-BTBT.Therefore,controlling the growth behavior of the semiconductor layer,therefore improving the coverage and crystallinity of the semiconductor layer is an effective way to fabricate high performance conjugated small molecule OTFT devices.