Qin Zhaotong, Pols Mike, Qin Minchao, Zhang Jianquan, Yan He, Tao Shuxia, Lu Xinhui
Department of Physics, The Chinese University of Hong Kong, Shatin 999077, Hong Kong SAR, People's Republic of China.
Materials Simulation and Modelling, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven, The Netherlands.
ACS Energy Lett. 2023 Jun 28;8(7):3188-3195. doi: 10.1021/acsenergylett.3c00853. eCollection 2023 Jul 14.
Quasi-two-dimensional (2D) Pb-Sn mixed perovskites show great potential in applications of single and tandem photovoltaic devices, but they suffer from low efficiencies due to the existence of horizontal 2D phases. Here, we obtain a record high efficiency of 18.06% based on 2D ⟨⟩ = 5 Pb-S mixed perovskites (-BAMA(PbSn)I, = 0.7), by optimizing the crystal orientation through a regulation of the Pb/Sn ratio. We find that Sn-rich precursors give rise to a mixture of horizontal and vertical 2D phases. Interestingly, increasing the Pb content can not only entirely suppress the unwanted horizontal 2D phase in the film but also enhance the growth of vertical 2D phases, thus significantly improving the device performance and stability. It is suggested that an increase of the Pb content in the Pb-Sn mixed systems facilitates the incorporation of -butylammonium (-BA) ligands in vertically oriented perovskites because of the reduced lattice strain and increased interaction between the organic ligands and inorganic framework. Our work sheds light on the optimal conditions for fabricating stable and efficient 2D Pb-Sn mixed perovskite solar cells.
准二维（2D）铅锡混合钙钛矿在单节和串联光伏器件应用中展现出巨大潜力，但由于水平二维相的存在，其效率较低。在此，我们通过调节铅/锡比例优化晶体取向，基于二维⟨⟩ = 5的铅锡混合钙钛矿（-BAMA(PbSn)I， = 0.7）获得了18.06%的创纪录高效率。我们发现富锡前驱体导致水平和垂直二维相的混合。有趣的是，增加铅含量不仅可以完全抑制薄膜中不需要的水平二维相，还能促进垂直二维相的生长，从而显著提高器件性能和稳定性。这表明，铅锡混合体系中铅含量的增加有利于丁基铵（-BA）配体掺入垂直取向的钙钛矿中，这是由于晶格应变减小以及有机配体与无机骨架之间的相互作用增强。我们的工作揭示了制备稳定高效的二维铅锡混合钙钛矿太阳能电池的最佳条件。
