Ma Xingjuan, Luo Hongqiang, Jiang Shusen, Zheng Lingling, Xue Hao, Li Xin
Pen-Tung Sah Institute of Micro-Nano Science and Technology, School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, China.
College of Materials, Xiamen University, Xiamen 361005, China.
ACS Appl Mater Interfaces. 2023 Aug 16;15(32):38444-38453. doi: 10.1021/acsami.3c06717. Epub 2023 Aug 1.
Nickel oxide (NiO) nanocrystals have been widely used in inverted (p-i-n) flexible perovskite solar cells (fPSCs) due to their remarkable advantages of low cost and outstanding stability. However, anion and cation impurities such as NO widely exist in the NiO nanocrystals obtained from calcinated nickel hydroxide (Ni(OH)). The impurities impair the photovoltaic performance of fPSCs. In this work, we report a facile but effective way to reduce the impurities within the NiO nanocrystals by regulating the Ni(OH) crystal phase. We add different alkalis, such as organic ammonium hydroxide and alkali metal hydroxides, to nickel nitrate solutions to precipitate layered Ni(OH) with different crystalline phase compositions (α and β mixtures). Especially, Ni(OH) with a high β-phase content (such as from KOH) has a narrower crystal plane spacing, resulting in fewer residual impurity ions. Thus, the NiO nanocrystals, by calcinating the Ni() with excess β phase from KOH, show improved performance in inverted fPSCs. A champion power conversion efficiency (PCE) of 20.42% has been achieved, which is among the state-of-art inverted fPSCs based on the NiO hole transport material. Moreover, the reduced impurities are beneficial for enhancing the fPSCs' stability. This work provides an essential but facile strategy for developing high-performance inverted fPSCs.
氧化镍（NiO）纳米晶体因其低成本和出色稳定性等显著优势，已被广泛应用于倒置（p-i-n）柔性钙钛矿太阳能电池（fPSC）中。然而，在由煅烧氢氧化镍（Ni(OH)₂）制得的NiO纳米晶体中，广泛存在诸如NO₃⁻等阴离子和阳离子杂质。这些杂质会损害fPSC的光伏性能。在这项工作中，我们报告了一种简便而有效的方法，即通过调控Ni(OH)₂的晶相来减少NiO纳米晶体中的杂质。我们向硝酸镍溶液中添加不同的碱，如有机氢氧化铵和碱金属氢氧化物，以沉淀出具有不同晶相组成（α和β混合物）的层状Ni(OH)₂。特别是，具有高β相含量的Ni(OH)₂（如由KOH制得的）具有更窄的晶面间距，从而残留的杂质离子更少。因此，通过煅烧含有来自KOH的过量β相的Ni(OH)₂所得到的NiO纳米晶体，在倒置fPSC中表现出了更好的性能。实现了20.42%的最佳功率转换效率（PCE），这在基于NiO空穴传输材料的最先进的倒置fPSC中处于领先水平。此外，杂质的减少有利于提高fPSC的稳定性。这项工作为开发高性能倒置fPSC提供了一种重要但简便的策略。
