Nayak Prem D, Dereli Büsra, Ohayon David, Wustoni Shofarul, Hidalgo Castillo Tania Cecilia, Druet Victor, Wang Yazhou, Hama Adel, Combe Craig, Griggs Sophie, Alsufyani Maryam, Sheelamanthula Rajendar, McCulloch Iain, Cavallo Luigi, Inal Sahika
Organic Bioelectronics Laboratory, Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
Physical Sciences and Engineering Division, KAUST Catalysis Center, KAUST, Thuwal 23955-6900, Saudi Arabia.
ACS Cent Sci. 2024 Nov 19;10(12):2229-2241. doi: 10.1021/acscentsci.4c00654. eCollection 2024 Dec 25.
Electron transporting (n-type) polymeric mixed conductors are an exciting class of materials for devices with aqueous electrolyte interfaces, such as bioelectronic sensors, actuators, and soft charge storage systems. However, their charge transport performance falls short of their p-type counterparts, primarily due to electrochemical side reactions such as the oxygen reduction reaction (ORR). To mitigate ORR, a common strategy in n-type organic semiconductor design focuses on lowering the lowest unoccupied molecular orbital (LUMO) level. Despite empirical observations suggesting a correlation between deep LUMO levels, low ORR, and enhanced electrochemical cycling stability in water, this relationship lacks robust evidence. In this work, we delve into the electrochemical reactions of n-type polymeric mixed conductors with varying LUMO levels and assess the impact of ORR on charge storage performance and organic electrochemical transistor (OECT) operation. Our results reveal a limited correlation between LUMO levels and ORR currents, as well as the electrochemical operational stability of the films. While ORR currents minimally contribute to OECT channel currents under fixed biasing conditions, n-type films self-discharge rapidly at floating potentials in a capacitor-like configuration. The density functional theory analysis, complemented by X-ray photoelectron spectroscopy, underscores the critical role of backbone chemistry in controlling O-related degradation pathways and device performance losses. These findings highlight the persistent challenge posed by ORR in n-type semiconductor design and advocate for shifting the focus toward exploring chemical moieties with limited O interactions to enhance operational stability and performance at n-type film/water interfaces.
电子传输（n型）聚合物混合导体是一类令人兴奋的材料，适用于具有水性电解质界面的器件，如生物电子传感器、致动器和软电荷存储系统。然而，它们的电荷传输性能不如p型同类材料，主要原因是存在诸如氧还原反应（ORR）等电化学副反应。为了减轻ORR的影响，n型有机半导体设计中的一个常见策略是专注于降低最低未占据分子轨道（LUMO）能级。尽管有经验观察表明深LUMO能级、低ORR与水中增强的电化学循环稳定性之间存在关联，但这种关系缺乏有力证据。在这项工作中，我们深入研究了具有不同LUMO能级的n型聚合物混合导体的电化学反应，并评估了ORR对电荷存储性能和有机电化学晶体管（OECT）操作的影响。我们的结果表明LUMO能级与ORR电流以及薄膜的电化学操作稳定性之间的相关性有限。虽然在固定偏置条件下ORR电流对OECT沟道电流的贡献最小，但n型薄膜在类似电容器的配置中于浮动电位下会迅速自放电。密度泛函理论分析辅以X射线光电子能谱，强调了主链化学在控制与氧相关的降解途径和器件性能损失方面的关键作用。这些发现凸显了ORR在n型半导体设计中带来的持续挑战，并主张将重点转向探索与氧相互作用有限的化学基团，以提高n型薄膜/水界面的操作稳定性和性能。
