基于TiO2/导电聚合物异质结型柔性紫外光探测器的性能调控与机理研究

To meet the demand for high performance, energy-saving, flexible and wearable devices, flexible heterojunction devices with a built-in potential difference acting as a driving force owing to the photovoltaic properties allows the device function efficiently for a long time without the need of an external energy supply. How to effectively solve the compromise for enhancing the photosensitivity as well as the response speed for photodetectors still remains a big challenge. Herein, a novel type of flexible heterojunction photodetector devices based on n-type anodic TiO2 nanostructures with various morphologies prepared on the flexible titanium substrates and p-type conducting polymers (doped-polyaniline) is developed. By optimizing the morphology and electrical conductivity of polyaniline, the overall photodetection performance can be accordingly improved. The proposal will conduct systematically study on the growth mechanism and regulation of anodic TiO2-based nanostructures, and the variation of the conductance of polyaniline at different doping levels to get more insight into the inherent relationships between structures、physical properties and the performances of the photoelectric devices. This study will enable the development of high performance, energy-saving and flexible UV photodetectors by a low-cost strategy due to inorganic/organic synergistic effects by combining the superior intrinsic carrier mobility of inorganic semiconductors and the tunable functionality of organic molecules, which might provide a new approach to realize hybrid inorganic/organic flexible devices from both theoretical and experimental aspects.

异质结型柔性紫外光探测器利用光伏特性，使器件在不施加偏压时也能高效稳定地工作，满足目前紫外探测技术节能化、集成化、柔性可穿戴的需求。而如何有效构筑pn结空间势垒区，以解决探测器量子效率和响应速度难以同时提升的矛盾一直是该领域的研究热点和难点。本项目拟采用阳极氧化法在柔性衬底上制备的TiO2纳米结构与掺杂态的导电聚合物构筑II型无机/有机异质结能带结构，避开p型掺杂的难题，通过调控聚合物的电导率来优化异质结型柔性器件的探测性能。深入研究TiO2纳米结构的生长机制，及不同掺杂程度下聚合物电导率的变化规律，进一步揭示器件性能、物性及微结构之间的内在构效关系；通过有机/无机复合的方法，充分利用无机半导体优异的本征载流子迁移率和有机分子性能可调节的优点，为新型无机/有机柔性器件的制备提供更加完善的实现途径和理论依据。

本项目紧紧围绕课题研究的总目标，在基于TiO2/导电聚合物异质结型柔性紫外探测器的性能调控与机理研究方面开展了较为深入和系统的研究工作，如通过构建无机-有机异质结实现自驱动性能，并进一步沉积Au纳米颗粒的热电子效应改善探测器的光电性能；利用酸处理提升导电聚合物电导率的策略改善探测器的响应度。首先选用一维的金属Ti微米纤维为基底，利用阳极氧化法原位生长制备TiO2纳米管(TiO2NTs)阵列，在通过真空浸渍法将导电聚合物P3HT (聚(3-乙基噻吩)均匀负载。得益于真空条件下强毛细作用力，有机物溶液充分渗透到纳米管间中，在TiO2NTs的外管壁上形成了一层薄且均匀的P3HT薄膜，实现了PN异质结有效接触面积的最大化以提供强大的内建电场。在器件构筑方面：以CNT纺线螺旋缠绕在Ti-TiO2/P3HT 微米纤维的表面，延伸部分作为外电极，Ti纤维的另一端抛光，作为内电极构筑纤维状的柔性器件。实验结果表明TiO2/P3HT纤维器件具有高自驱动性能、宽谱响应、响应速度快，弯曲状态下稳定性好等优点。进一步利用磁控溅射法负载Au纳米颗粒有利于提高器件的响应度和光选择性，实现了器件的探测性能的极大提升：在0 V 时的响应度提高了约700%，器件的紫外-可见光抑制比也达到了17，表明Au/TiO2/P3HT器件是一种自驱动型柔性紫外探测器。在此基础上，将该设计理念推广到其他两种无机/有机异质结探测器中：TiO2/PEDOT:PSS 和TiO2/PANI；通过PN异质结的内在驱动实现了零偏压下的自驱动光电探测性能。在该基金的支持下已经发表SCI论文9篇，申请中国发明专利2项。参加国际学术会议1次并作专题报告，协助举办国际会议1次并担任分会场主持人，与国内外多个课题组开展合作交流研究。该国家基金参与培养5名硕士生，1名博士生。