Gicevičius Mindaugas, James Ann Maria, Reicht Lukas, McIntosh Nemo, Greco Alessandro, Fijahi Lamiaa, Devaux Félix, Mas-Torrent Marta, Cornil Jérôme, Geerts Yves Henri, Zojer Egbert, Resel Roland, Sirringhaus Henning
Optoelectronics Group, Cavendish Laboratory, University of Cambridge JJ Thomson Avenue Cambridge CB3 0HE UK
Institute of Solid State Physics, NAWI Graz, Graz University of Technology Petersgasse 16 8010 Graz Austria.
Mater Adv. 2024 Jul 10;5(15):6285-6294. doi: 10.1039/d4ma00594e. eCollection 2024 Jul 29.
Side-chain engineering in molecular semiconductors provides a versatile toolbox for precisely manipulating the material's processability, crystallographic properties, as well as electronic and optoelectronic characteristics. This study explores the impact of integrating hydrophilic side chains, specifically oligoethylene glycol (OEG) units, into the molecular structure of the small molecule semiconductor, 2,7-bis(2(2-methoxy ethoxy)ethoxy) benzo[]benzo[4,5] thieno[2,3-] thiophene (OEG-BTBT). The investigation includes a comprehensive analysis of thin film morphology and crystallographic properties, along with the optimization of deposition parameters for improving the device performance. Despite the anticipated benefits, such as enhanced processability, our investigation into OEG-BTBT-based organic field-effect transistors (OFETs) reveals suboptimal performance marked by a low effective charge carrier mobility, a low on/off ratio, and a high threshold voltage. The study unveils bias stress effects and device degradation attributed to the high ionization energy of OEG-BTBT alongside the hydrophilic nature of the ethylene-glycol moieties, which lead to charge trapping at the dielectric interface. Our findings underscore the need for a meticulous balance between electronic properties and chemical functionalities in molecular semiconductors to achieve stable and efficient performance in organic electronic devices.
分子半导体中的侧链工程提供了一个多功能工具箱，用于精确控制材料的可加工性、晶体学性质以及电子和光电特性。本研究探讨了将亲水性侧链，特别是低聚乙二醇（OEG）单元，整合到小分子半导体2,7-双（2-（2-甲氧基乙氧基）乙氧基）苯并[1,2-b：4,5-b']二噻吩（OEG-BTBT）分子结构中的影响。该研究包括对薄膜形态和晶体学性质的全面分析，以及优化沉积参数以提高器件性能。尽管有诸如增强可加工性等预期好处，但我们对基于OEG-BTBT的有机场效应晶体管（OFET）的研究显示其性能欠佳，表现为有效电荷载流子迁移率低、开/关比低和阈值电压高。该研究揭示了由于OEG-BTBT的高电离能以及乙二醇部分的亲水性导致的偏置应力效应和器件退化，这会导致电荷在介电界面处俘获。我们的研究结果强调，在分子半导体中，电子性质和化学功能之间需要进行细致的平衡，以在有机电子器件中实现稳定和高效的性能。
