Direct imaging and probing of polymer electrolyte/luminescent conjugated polymer mixed ionic/electronic conductors

聚合物电解质是一种固态离子导体，是某些燃料电池、锂离子电池和电致变色器件的关键组成部分。共轭发光聚合物是一种有机半导体，是聚合物发光二极管、聚合物薄膜晶体管、聚合物光伏太阳能电池等新兴“塑料”电子器件的有效成分。结合这两种材料，由于电子和离子电荷之间的相互作用，产生了一种发光聚合物混合离子/电子导体（MIEC）。在所谓的聚合物发光电化学电池（LEC）中首次研究了发光聚合物MIEC。LEC的基本工作机制涉及到发光聚合物的p-和n-原位电化学掺杂以及动态发光p-n结的形成。2003年，高博士的团队首次展示了具有毫米级电极间距的平面LECs。极大且完全暴露的电极间隙允许具有高时间和空间分辨率的延时荧光成像。首次在相机上捕捉到p-和n-掺杂的动态过程以及结的形成过程。高博士随后的研究表明，复杂的掺杂和电致发光过程受到工作电压和温度、盐类型、电极功函数、金属颗粒的存在、薄膜形态和热历史的强烈影响。在拟议的研究中，高博士将使用微操纵低温探针站（通过NSERC RTI资助购买）直接测量超大平面LEC的电导率和电势分布。光纤探头将通过测量感应光电流或光电压来检测内置电场或电势。提出的研究将解决与发光共轭聚合物、聚合物电解质及其混合物的性质有关的基本问题。研究结果将提高我们对LEC的理解，并可能导致更高效的基于聚合物的发光器件、光伏太阳能电池和可充电电池。

A polymer electrolyte is a solid-state ionic conductor and a key component of certain fuel cells, lithium ion batteries and electrochromic devices. A conjugated luminescent polymer is an organic semiconductor and the active component of polymer light-emitting diodes, polymer thin film transistors, polymer photovoltaic solar cells and other emerging "plastic" electronic devices. Combining the two materials creates a luminescent polymer mixed ionic/electronic conductor (MIEC) rich in interesting physics due to the interaction between electronic and ionic charges. A luminescent polymer MIEC was first studied in the so-called polymer light-emitting electrochemical cell (LEC). The fundamental operating mechanism of an LEC involves in situ electrochemical p- and n-doping of the luminescent polymer and the formation of a dynamic, light-emitting p-n junction. In 2003 Dr. Gao's group first demonstrated planar LECs with millimeter-sized interelectrode spacing. The extremely large and fully exposed interelectrode gap allows for time-lapse fluorescence imaging with high temporal and spatial resolution. For the first time the dynamic p- and n-doping as well as the junction formation processes were captured on camera. Dr. Gao's subsequent studies showed that the complex doping and electroluminescence processes were strongly affected by operating voltage and temperature, salt type, electrode work function, the presence of metallic particles, film morphology and thermal history. In the proposed research Dr. Gao will use a micro-manipulated cryogenic probe station (purchased through a NSERC RTI grant) to directly measure the electrical conductivity and electrical potential distribution across an extremely large planar LEC. A fiber optics probe will be used to detect the built-in electrical field or potential by measuring the induced photocurrent or photovoltage. The proposed research will address fundamental questions related to the properties of luminescent conjugated polymers, polymer electrolytes and their mixtures. The results will improve our understanding of LEC and may lead to more efficient polymer-based light-emitting devices, photovoltaic solar cells and rechargeable batteries.