Mohanraj John, Samanta Bipasa, Almora Osbel, Escalante Renán, Marsal Lluis F, Jenatsch Sandra, Gadola Arno, Ruhstaller Beat, Anta Juan A, Caspary Toroker Maytal, Olthof Selina
Department of Chemistry, University of Cologne, Greinstrasse 4-6, Cologne 50939, Germany.
Department of Materials Science and Engineering, Technion─Israel Institute of Technology, Haifa 3600003, Israel.
ACS Appl Mater Interfaces. 2024 Aug 14;16(32):42835-42850. doi: 10.1021/acsami.4c06709. Epub 2024 Aug 1.
Nonstoichiometric nickel oxide (NiO) is one of the very few metal oxides successfully used as hole extraction layer in p-i-n type perovskite solar cells (PSCs). Its favorable optoelectronic properties and facile large-scale preparation methods are potentially relevant for future commercialization of PSCs, though currently low operational stability of PSCs is reported when a NiO hole extraction layer is used in direct contact with the perovskite absorber. Poorly understood degradation reactions at this interface are seen as cause for the inferior stability, and a variety of interface passivation approaches have been shown to be effective in improving the overall solar cell performance. To gain a better understanding of the processes happening at this interface, we systematically passivated specific defects on NiO with three different categories of organic/inorganic compounds. The effects on NiO and the perovskite (MAPbI) deposited on top were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Here, we find that the perovskite's structural stability and film formation can be significantly affected by the passivation treatment of the NiO surface. In combination with density functional theory (DFT) calculations, a likely origin of NiO-perovskite degradation interactions is proposed. The surface passivated NiO layers were incorporated into MAPbI-based PSCs, and the influence on device performance and operational stability was investigated by current-voltage (-) characterization, impedance spectroscopy (IS), and open circuit voltage decay (OCVD) measurements. Interestingly, we find that a superior structural stability due to interface passivation must not relate to high operational stability. The discrepancy comes from the formation of excess ions at the interface, which negatively impacts all solar cell parameters.
非化学计量比的氧化镍（NiO）是极少数成功用作p-i-n型钙钛矿太阳能电池（PSC）空穴提取层的金属氧化物之一。其良好的光电性能和简便的大规模制备方法对PSC的未来商业化具有潜在意义，尽管目前报道称当NiO空穴提取层与钙钛矿吸收层直接接触时，PSC的运行稳定性较低。人们认为该界面处难以理解的降解反应是稳定性较差的原因，并且已证明多种界面钝化方法在改善整体太阳能电池性能方面是有效的。为了更好地理解该界面处发生的过程，我们用三类不同的有机/无机化合物系统地钝化了NiO上的特定缺陷。使用X射线光电子能谱（XPS）、X射线衍射（XRD）和扫描电子显微镜（SEM）研究了对NiO以及沉积在其上的钙钛矿（MAPbI）的影响。在此，我们发现钙钛矿的结构稳定性和成膜会受到NiO表面钝化处理的显著影响。结合密度泛函理论（DFT）计算，提出了NiO-钙钛矿降解相互作用的可能起源。将表面钝化的NiO层纳入基于MAPbI的PSC中，并通过电流-电压（-）表征、阻抗谱（IS）和开路电压衰减（OCVD）测量研究了对器件性能和运行稳定性的影响。有趣的是，我们发现由于界面钝化导致的优异结构稳定性不一定与高运行稳定性相关。这种差异源于界面处过量离子的形成，这对所有太阳能电池参数都有负面影响。
