Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells
Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells
复制标题
界面分子取向对钙钛矿太阳能电池功率转换效率的影响
DOI：
10.1021/jacs.6b10651
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发表时间：
2017
影响因子：
15
通讯作者：
Chen Zhan
中科院分区：
文献类型：
--
作者：
Xiao Minyu;Joglekar Suneel;Zhang Xiaoxian;Jasensky Joshua;Ma Jialiu;Cui Qingyu;Guo L Jay;Chen Zhan
各种各样的载流子动力学，如输运，分离和提取，发生在平面异质结太阳能电池的界面。这些因素会影响设备的整体性能。因此，了解各种器件中埋藏的界面分子结构以及界面结构与功能之间的关系变得越来越重要。目前的薄膜表征技术，如x射线衍射、截面扫描电子显微镜和紫外-可见吸收光谱等，无法提供隐藏界面所需的分子结构信息。本研究通过控制钙钛矿太阳能电池中空穴传输层（HTL）的结构，并应用表面/界面敏感非线性振动光谱技术（和频产生振动光谱（SFG）），成功探测了埋藏界面处的分子结构，并将其结构特征与太阳能电池性能联系起来。在这里，埋藏的钙钛矿（光活性层）/PT （html）界面上的边对（垂直于界面）聚噻吩（PT）界面分子取向显示了两倍以上的功率转换效率（PCE）的躺卧（切向）PT界面取向。界面分子结构的差异是通过改变PT衍生物的烷基侧链长度来实现的，其中烷基侧链较短的PT比烷基侧链较长的PT具有更高的PCE，界面取向为边朝上。由于PT层内的带隙排列和体积结构相似，因此认为各种PT衍生物的界面分子结构变化（即取向差异）是导致钙钛矿太阳能电池PCE差异的根本原因。
A wide variety of charge carrier dynamics, such as transport, separation, and extraction, occur at the interfaces of planar heterojunction solar cells. Such factors can affect the overall device performance. Therefore, understanding the buried interfacial molecular structure in various devices and the correlation between interfacial structure and function has become increasingly important. Current characterization techniques for thin films such as X-ray diffraction, cross section scanning electronmicroscopy, and UV–visible absorption spectroscopy are unable to provide the needed molecular structural information at buried interfaces. In this study, by controlling the structure of the hole transport layer (HTL) in a perovskite solar cell and applying a surface/interface-sensitive nonlinear vibrational spectroscopic technique (sum frequency generation vibrational spectroscopy (SFG)), we successfully probed the molecular structure at the buried interface and correlated its structural characteristics to solar cell performance. Here, an edge-on (normal to the interface) polythiophene (PT) interfacial molecular orientation at the buried perovskite (photoactive layer)/PT (HTL) interface showed more than two times the power conversion efficiency (PCE) of a lying down (tangential) PT interfacial orientation. The difference in interfacial molecular structure was achieved by altering the alkyl side chain length of the PT derivatives, where PT with a shorter alkyl side chain showed an edge-on interfacial orientation with a higher PCE than that of PT with a longer alkyl side chain. With similar band gap alignment and bulk structure within the PT layer, it is believed that the interfacial molecular structural variation (i.e., the orientation difference) of the various PT derivatives is the underlying cause of the difference in perovskite solar cell PCE.