Chen Jianxia, Dong Zhixiang, Wang Qi, Han Zhijing, Sun Haofeng, Li Yuzhan, Wu Ying, Zhan Xiaozhi, Zhu Tao, Endoh Maya, Koga Tadanori, Jiang Naisheng
Key Laboratory of Advanced Materials and Devices for Post-Moore Chips, Ministry of Education, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Spallation Neutron Source Science Center, Dongguan 523803, China.
ACS Appl Mater Interfaces. 2024 Oct 5. doi: 10.1021/acsami.4c11049.
We investigate the irreversible adsorption of poly(3-hexylthiophene) (P3HT) polymer thin films on silicon dioxide/silicon (SiO/Si) substrates during thermal annealing at a temperature below the melting temperature () but far above the glass transition temperature (), i.e., ≪ = 170 °C < , and its effect on their crystalline ordering and charge transport properties. It was found that short-time annealing enhances the molecular ordering of P3HT films, while prolonged thermal annealing gradually disrupts the crystalline structures and reduces the overall crystallinity of the film. Concurrently, thermal annealing at this temperature facilitates the slow irreversible adsorption of P3HT chains at the polymer-solid interface, resulting in the formation of a 1.7 -thick (∼18 nm thick) adsorbed layer on SiO/Si substrates that is fully amorphous and contains a large fraction of loosely adsorbed chains. We postulate that such irreversible adsorption is responsible for the reduced crystalline packing of P3HT at the polymer-solid interface at ≪ < , which further disrupts the molecular ordering of the entire 46 nm thick P3HT film by a long-range perturbation effect. Electrical measurements using an organic field-effect transistor (OFET) device reveal that the enhanced charge carrier mobility of P3HT films correlates with an optimized annealing time at ≪ < , which achieves a balance between maximizing molecular ordering and minimizing the impact of irreversible chain adsorption. These findings provide new insights into the underlying mechanism of thermal annealing in tailoring the structure and property of conjugated polymer thin films prepared on solid substrates.
我们研究了聚（3 - 己基噻吩）（P3HT）聚合物薄膜在低于熔点（）但远高于玻璃化转变温度（），即 ≪ = 170 °C < 的温度下热退火过程中在二氧化硅/硅（SiO/Si）衬底上的不可逆吸附，以及其对薄膜结晶有序性和电荷传输性能的影响。研究发现，短时间退火增强了P3HT薄膜的分子有序性，而长时间热退火会逐渐破坏晶体结构并降低薄膜的整体结晶度。同时在此温度下的热退火促进了P3HT链在聚合物 - 固体界面的缓慢不可逆吸附，导致在SiO/Si衬底上形成一个1.7 厚（约18 nm厚）的吸附层，该吸附层完全无定形且包含很大一部分松散吸附的链。我们推测这种不可逆吸附是导致在 ≪ < 时P3HT在聚合物 - 固体界面处结晶堆积减少的原因，这通过长程扰动效应进一步破坏了整个46 nm厚P3HT薄膜的分子有序性。使用有机场效应晶体管（OFET）器件进行的电学测量表明，P3HT薄膜增强的载流子迁移率与在 ≪ < 时的优化退火时间相关，该优化退火时间在最大化分子有序性和最小化不可逆链吸附影响之间实现了平衡。这些发现为热退火在定制固体衬底上制备的共轭聚合物薄膜的结构和性能方面的潜在机制提供了新的见解。
