纳米红外光谱与光电性质关联成像新方法及在工况下薄膜光电转换体系的应用

Surface and interfaces are of great importance in thin-film light-conversion systems such as perovskite solar cells (PSCs). There are many fundamental questions related to interfacial physical chemistry of these systems. For example, how the defects in grains and grain boundaries in the perovskite layer, and/or interlayer structures of a PSC, in the length scale ranged from sub-nanometer to tens of nanometer, affect the photoelectric conversion efficiency (PCE) and influence the stabilities of the PSCs are remained unknown. To our best knowledge, however, there are no effective methods for correlated imaging of nanoscale chemical structures and photoelectric properties. Here, we propose to correlate the local chemical structures by measuring the nanoscale infrared (nanoIR) spectroscopy in the PeakForce Tapping (PFT) mode of an atomic force microscope (AFM), with the nanoscale surface photocurrent measured by photocurrent AFM (pcAFM), and with nanoscale surface potential measured by Kelvin probe force microscopy (KPFM). However, several difficulties should be overcome by developing several new approaches: (1) All the three advanced AFM modes are developed to work in the same probe-controlling mode, PFT, in order to solve the mutual consistency problem of the three modes; (2) The illumination of light, the measurement of nanoIR, pcAFM and KPFM will be sequentially controlled to make sure that all measurements are performed in the same micro region of the same sample at the same states; (3) nanoIR imaging will be correlated with pcAFM and KPFM imaging taking nano-mechanical imaging as reference; (4) The in situ AFM cell is developed with the capability to control the humidity, temperature, the partial pressure of O2 and illuminating light in the cell, and to compatibly measure nanoIR, pcAFM and KPFM. With the help of aforementioned new inventions, we are going to systematically establish a new method for correlated imaging of nanoscale infrared spectroscopy and photoelectric properties, revealing the structure-function relationship in nanoscale. Finally, the working mechanism and the aging mechanism of PSCs in nanoscale will be studied. The methods in this proposal could be straightforwardly extended to more general application field such as organic photovoltaics and semiconductor photocatalysis.

钙钛矿太阳能电池（PSCs）等薄膜光电转换体系广泛存在着界面物理化学相关的基本科学问题，如钙钛矿层内晶粒的缺陷和晶界结构及层间界面结构如何影响PSCs光电转化效率和稳定性？迄今缺乏有效关联纳米分辨的化学结构与光电性质的测量方法。针对该关联成像方法存在的瓶颈问题，本项目拟将峰值力纳米红外光谱技术与峰值力光导电原子力显微镜、峰值力开尔文探针力显微镜相关联，以破解探针驱动方式兼容性难题；发展可见/红外光激发-纳米红外测量-光电性质测量的时序控制方法，以实现同样品同状态的关联测量；设计以纳米力学为成像参考的结构-物性关联成像算法；研制可控湿度、温度和光，可测纳米红外和光电性质的AFM原位池，系统建立纳米红外光谱与光电性质关联成像新方法，并应用到尺寸在几纳米到几十纳米的界面构效关系研究，揭示工况下PSCs微观工作机理与陈化机制。该方法还可拓展于研究有机太阳能电池、半导体光催化等其他太阳能源材料体系。

纳米分辨红外光谱和纳米尺度如光电性质关联成像技术对于揭示多晶材料的纳米尺度光电材料构效关系十分重要。为了一方面要建立基于原子力显微镜的纳米红外光谱-纳米光电压关联成像测量方法，也需要进一步提高纳米红外光谱的灵敏度、发展高光谱高速成像智能算法等。为此，项目组完成了纳米分辨红外光谱-光生开尔文探针力显微镜（KPFM）关联成像方法的搭建，实现了纳米尺度自由载流子密度的定量测量，揭示了多晶钙钛矿材料晶界处能带弯曲导致多晶比单晶钙钛矿材料更有利于光生电子-空穴分离，且光生电子主要分布在晶界处的微观机制（Light: Sci Appl, 2021, 10, 84）；发明了石墨烯包覆光学介质原子力显微镜探针，实现了纳米分辨红外光谱的增强因子比优选商用探针高1~2个数量级，还可应用于耐磨型导电原子力显微镜（发明专利申请号202110996148.5）；设计并构筑了一种同时支持多波段共振的纳米桥联的菱形天线，揭示了该天线中纳米桥结构支持高阶光学模式共振的物理机制，为发展金属基微纳结构增强红外光谱提供了新思路（Opto-Electron Adv, 2021, 4, 210076）；系统发展了分子振动-红外等离激元的耦合强度调控等离激元增强红外吸收光谱线型的理论，提出了等离激元辅助分子间长程相干相互作用的机制，为在纳米尺度调控缀饰振动激发态提供了新思路（Natl Sci Rev, 2020, 7, 1228-1238）；发明了全色锐化算法结合卷积神经网络的高速成像智能算法，实现了在高保真图象（>99%）前提下，将高光谱成像速度提升近100倍，可广泛应用于数据立方体高速采集（发明专利申请号202111281935.8），采用类似算法大幅提升了AFM纳米形貌成像速度（Anal Chem, 2022, 94, 5041-5047）；发展了可精准计算单晶电极/溶液电化学界面红外光谱和拉曼光谱的量子化学计算方法（Chem Sci, 2020, 11, 1425-1430，J Electroanal Chem, 2021, 896, 115337），解决了近40年界面电化学领域的一个公认未解的界面结构鉴定难题，即Au(111)/硫酸界面电化学结构相变（J Am Chem Soc, 2020, 142, 9439-9446）。