有机场效应晶体管的工作稳定性：偏压应力效应的机理研究

Organic field effect transistors (OFETs) have great potential in numerous applications such as smart cards, flexible displays and sensors, and the operation stability of OFETs is critically significant in all the practical applications. The bias stress induced current instability in OFETs is known as the bias stress effect, and understanding the microscopic mechanism of the bias stress effect is the key to improve the operation stability of OFETs. We propose that the bias stress effect is correlated to the charge trapping in the deep trap states, which is responsible for the current instability in OFETs. This proposal is focusing on the elucidation of the correlation between the deep trap states and the bias stress effect, and will pursue systematical studies on the bias stress effect in P-type, N-type and ambipolar OFETs. Upon comparing and analyzing the dependences of the bias stress effect on different factors such as contact, grain boundary, interface chemistry, gate bias and measuring temperature, the spatial and energetic distribution of the deep trap states in OFETs can be clarified. This proposal will combine experimental investigation and theoretical modeling to elucidate the microscopic mechanism of the bias stress effect in OFETs, and the results are expected to give guidance towards high-performance P-type, N-type and ambipolar OFETs with high operation stability.

有机场效应晶体管在信息电子等多个领域具有广阔的应用前景，其工作稳定性在实际应用中显得至关重要。有机场效应晶体管在工作状态下的电流不稳现象被称为偏压应力效应，理解偏压应力效应的机理是提高器件工作稳定性的关键。本课题组提出，偏压应力效应的机理与载流子被电荷深陷阱态所捕获有关，微观上深陷阱态的电荷捕获与电荷释放过程决定了宏观上器件的工作稳定性。本项目围绕电荷深陷阱态如何影响器件的工作稳定性这一关键科学问题，系统性地研究P型、N型以及双极型有机场效应晶体管的偏压应力效应。通过比较和分析偏压应力效应对电极接触、晶界密度、界面化学、栅极偏压与测量温度等诸多因素的依赖性，明确电荷深陷阱态在空间上以及在能量上的分布。结合器件行为研究与微观机理研究，构建物理模型，认识器件中深陷阱态电荷捕获与电荷释放的动态过程，从而阐明偏压应力效应的机理。本项目将为实现高性能高稳定性的单极型与双极型有机场效应晶体管指明方向。

本项目的研究工作按照研究计划顺利执行与完成。在项目资助下，已在Applied Physics Letters、Advanced Electronic Materials、Organic Electronics等国际学术期刊上发表SCI论文33篇（全部为通讯作者）。在本项目资助下，共培养了3名博士研究生，9名硕士研究生。在机理研究方面，本项目分别给出了针对P型、N型以及双极型有机场效应晶体管的物理模型，阐明了有机场效应晶体管偏压应力效应的微观机理，并以此为基础找到了提高器件工作稳定性的关键途径。首先，可通过栅极介质层的材料选择和表面修饰来改善活性层形貌和减少界面缺陷态，从而压制器件的偏压应力效应；其次，可通过引入界面缓冲层或表面掺杂层来提高器件的工作稳定性。在器件研究方面，开展了低电压有机场效应晶体管的工作稳定性研究，实现了具有高工作稳定性的柔性低电压有机场效应晶体管；此外，开展了有机场效应晶体管非易失性存储器的存储稳定性研究和存储机理研究，实现了具有高存储稳定性的有机场效应晶体管非易失性存储器。本项目为解决有机场效应晶体管在实际应用中的工作稳定性问题提供了重要信息。