The deposition of large ammonium cations onto perovskite surfaces to passivate defects and reduce contact recombination has enabled exceptional efficiency and stability in perovskite solar cells. These ammonium cations can either assemble as a thin molecular layer at the perovskite surface or induce the formation of a low-dimensional (usually two-dimensional) perovskite capping layer on top of the three-dimensional perovskite. The formation of these two different structures is often overlooked by researchers, although they impact differently on device operation. In this Review, we seek to distinguish between these two passivation layers. We consider the conditions needed for the formation of low-dimensional perovskite and the electronic properties of the two structures. We discuss the mechanisms by which each method improves photovoltaic efficiency and stability. Finally, we summarize the knowledge gaps that need to be addressed to better understand and optimize ammonium cation-based passivation strategies.

将大铵阳离子沉积到钙钛矿表面以钝化缺陷并减少接触复合，使得钙钛矿太阳能电池具有卓越的效率和稳定性。这些铵阳离子可以在钙钛矿表面组装为薄分子层，也可以诱导在三维钙钛矿顶部形成低维（通常是二维）钙钛矿覆盖层。这两种不同结构的形成经常被研究人员忽视，尽管它们对设备操作的影响不同。在这篇综述中，我们试图区分这两个钝化层。我们考虑了低维钙钛矿形成所需的条件以及两种结构的电子特性。我们讨论了每种方法提高光伏效率和稳定性的机制。最后，我们总结了需要解决的知识差距，以更好地理解和优化基于铵阳离子的钝化策略。