界面调控对有机非富勒烯太阳能电池工作过程的影响研究

The operation of organic bulk heterojunction (BHJ) solar cells is concurrently governed by hulk opto-electronic and interfacial properties. In recent years, our Chinese researchers have made impressive breakthrough in molecular design of non-fullerene electron acceptors and power conversion efficiency (PCE) in relevant devices. Generally, non-fullerene acceptors are featured by the tunability in energetics, relative low exciton binding energy, high crystallinity and the presence of function groups with strong polarity etc. However, to date the fundamental knowledge on how the interface properties influence basic working processes in operational solar cells remains poorly understood. To gain more insights into the interface property-device performance relationships and realize improved PCEs, in this proposal, based on the established knowledge and understandings on fullerene BHJ systems, we plan to control the electronic structure at the BHJ /electrode interface, interfacial dipole interaction and surface chemistry through interface engineering in non-fullerene solar cells. With the interface modifications, we will focus on investigating the resultant changes in internal electrical field, energetic disorder, surface traps and interfacial energetic barrier in devices and elucidate how the interface properties impact exciton dissociation, charge carrier transport, recombination and extraction in operational solar cells by means of surface analysis and transient/steady-state electrical characterizations. We aim the develop a general and effective interface strategy that allows to tailor the device characteristics and ultimate PCEs. With this proposed study, we expect to frame a guideline for improving the materials design and device engineering for organic BHJ solar cells using non-fullerene acceptors.

有机太阳能电池工作过程受活性层和界面性质的共同影响。近年来，我国在非富勒烯受体分子设计以及相应的电池性能方面取得了重大突破，非富勒烯体系具有能级结构可调、较低的激子解离能、高结晶性及含强极性基团等特点。然而，目前我们对界面性质如何影响非富勒烯体系器件的基本工作过程尚不十分清楚。为了进一步揭示界面性质-器件工作过程之间的科学规律，提高非富勒烯器件转化效率，申请人拟借鉴在富勒烯体系积累的理论基础和研究手段，利用界面调控非富勒烯体异质结/电极界面表面表面功函数、界面偶极和表面化学基团等表面性质，通过表面分析、稳态/瞬态光电测试等表征方法，研究器件的内建电场、活性层能量无序度、界面能量势垒/缺陷等物理性质对非富勒烯太阳能电池器件的激子分离、电荷传输以及电荷收集/复合等工作过程的影响。建立有利于改善非富勒烯太阳能电池性能的界面调控方法，为新型有机光伏材料设计和器件优化提供参考。

近年来，我国在有机太阳能电池研究方面取得了突飞猛进的进展，在国际上属于领先地位。界面性质是影响有机太阳能电池的关键因素之一。本项目针对溶液法制备的有机太阳能电池的界面调控展开了系列研究工作：1）优化了界面修饰对器件内建电场的调控能力，利用原位电化学合成的方法，选用共轭聚合物阳极界面材料，改善了空穴传输层的功函数，增大了器件的内建电场，提高了器件电荷收集效率；2）通过界面掺杂的手段，钝化了活性层表面缺陷，提高了界面层的电导率，改善了器件电荷收集效率；3）通过调控界面层表面能优化了活性层形貌，显著提高了器件的填充因子和转换效率，探索了活性层堆积方式与界面层表面能选择之间的联系，揭示了界面层表面能纳米级非均一性分布对活性层形貌和器件性能的影响。上述研究成果拓展了应用于有机太阳能电池空穴传输层的新材料，丰富了对有机太阳能电池界面修饰的调控手段，加深了对界面调控对器件相关器件物理工作过程影响的理解水平，有助于实现高效稳定的有机太阳能电池。在本项目支持下，多次参与相关学术交流，在有机光电材料与器件领域为国家培养了多名的科研人员，项目负责人共发表文章42篇，其中以通讯作者身份发表了30篇研究论文，包括5篇Adv. Mater.，1篇Joule，1篇Matter，3篇Nano Energy，3篇J. Mater. Chem. A等。