Polymer photonic devices based on mixed ionic/electronic conductors: device and materials physics

半导体光子器件，如发光二极管（LED），太阳能电池，光电二极管和二极管激光器是不可或缺的，在我们的技术和信息驱动的世界。虽然这些器件仍然主要基于硅或III-V族化合物，但各种有机半导体已经成为下一代应用的潜在候选者，这些应用需要更高的功能和更低的能耗。半导体聚合物是特别有吸引力的，因为它们具有聚合物材料的机械和加工优点，以及光学和电学上令人感兴趣。* * 为了使“塑料电子”成为现实，聚合物半导体不仅需要更好地理解和充分利用它们的纯形式，而且还需要掺杂。"导电聚合物"（2000年诺贝尔化学奖）领域的出现是因为发现聚乙炔在化学掺杂后表现出极大的导电性。 迄今为止，大多数聚合物器件都是基于原始聚合物。一个例外是聚合物发光电化学电池（LEC），其活性层是混合离子/电子导体（MIEC）。LEC的MIEC在操作期间原位电化学掺杂，并且在不同掺杂区域之间形成发光p-n或p-i-n结。由于掺杂，LEC具有许多期望的器件特性。MIEC器件（如LEC）面临的主要挑战是其较差的工作寿命和缺乏对底层物理的理解。这在很大程度上是由于MIEC器件的复杂性质，其具有至少四种可以相互作用的不同电荷载流子。* * 在我们拟议的研究中，将深入探索和研究各种聚合物MIEC器件，以应对挑战。特别是，我们将进行前所未有的，协调一致的扫描光电流，光致发光和吸收测量极大的，冷冻平面细胞，以更好地了解MIEC结的电子结构。 此外，我们努力实现可用于实际应用的持久MIEC器件。拟议的研究将建立在我的团队在MIEC发光电池和光伏电池方面的丰富经验基础上，近年来在国际顶级期刊上发表了近30篇论文。我的团队还开发了一套强大的实验技术，非常适合研究MIEC设备。这些技术包括延时荧光成像、冻结结和受控结弛豫、电导率和电势的扫描电探测以及协同扫描光电流和光致发光探测技术。拟议的研究为HQP的培训提供了极好的机会，这将使他们为学术研究或工业研发的职业生涯做好准备。**

Semiconductor photonic devices such as light-emitting diodes (LEDs), solar cells, photodiodes, and diode lasers are indispensible in our technology- and information-driven world. While these devices are still mainly based on silicon or group III-V compounds, various organic semiconductors have emerged as potential candidates for next-generation applications that require even higher functionality and less energy consumption. Semiconducting polymers are especially attractive because they have the mechanical and processing advantages of polymeric materials as well as being optically and electrically interesting. ******To make "plastic electronics" a reality, polymer semiconductors need to be better understood and fully exploited not only in their pure form, but also when "doped." The field of "conductive polymers" (2000 Nobel Prize in Chemistry) came into existence when polyacetylene was discovered to exhibit vastly improved conductivity when chemically doped. Most polymer devices to date are based on pristine polymers. An exception is the polymer light-emitting electrochemical cell (LEC), whose active layer is a mixed ionic/electronic conductor (MIEC). The MIEC of an LEC is electrochemically doped in situ during operation, and a light-emitting p-n or p-i-n junction is formed between the differently doped regions. The LECs possess many desirable device characteristics as a result of doping. The chief challenges facing MIEC devices such as LECs is their inferior operational lifetime and the lack of understanding of the underlying physics. This is in large part due to the complex nature of MIEC devices, which possess at least four different charge carriers that can interact. ******In our proposed research, various polymer MIEC devices will be explored and investigated in depth in order to deal with the challenges. In particular, we will perform unprecedented, concerted scanning photocurrent, photoluminescence and absorption measurements of extremely large, frozen planar cells in order to better understand the electronic structure of MIEC junctions.  In addition, we strive to achieve long lasting MIEC devices ready for practical applications. The proposed research will build on my group's extensive experience working on MIEC light-emitting cells and photovoltaic cells that has resulted in nearly 30 publications in top international journals in recent years. My group also developed a suite of powerful experimental techniques ideally suited for the study of MIEC devices. These include time-lapse fluorescence imaging, frozen-junction and controlled junction relaxation, scanning electrical probing of conductivity and electric potential, and concerted scanning photocurrent and photoluminescence probing techniques. The proposed research offers excellent opportunities for the training of HQPs that will prepare them for a career in academic research or industrial R&D. **