Li Weilun, Yuan Qimu, Chen Yinan, Lilly Joshua R S, Filip Marina R, Herz Laura M, Johnston Michael B, Etheridge Joanne
School of Physics and Astronomy, Monash University, Melbourne, VIC, 3800, Australia.
Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK.
Adv Mater. 2025 Aug;37(34):e2501788. doi: 10.1002/adma.202501788. Epub 2025 Jun 16.
The perovskite semiconductor, CsPbI, holds excellent promise for solar cell applications due to its suitable bandgap. However, achieving phase-stable CsPbI solar cells with high power conversion efficiency remains a major challenge. Ruddlesden-Popper (RP) defects have been identified in a range of perovskite semiconductors, including CsPbI. However, there is limited understanding as to why they form or their impact on stability and photophysical properties. Here, the prevalence of RP defects is increased with increased Cs-excess in vapor-deposited CsPbI thin films while superior structural stability but inferior photophysical properties are observed. Significantly, using electron microscopy, it is found that the atomic positions at the planar defect are comparable to those of a free surface, revealing their role in phase stabilization. Density functional theory (DFT) calculations reveal the RP planes are electronically benign, however, antisites observed at RP turning points are likely to be malign. Therefore it is proposed that increasing RP planes while reducing RP turning points offers a breakthrough for improving both phase stability and photophysical performance. The formation mechanism revealed here can apply more generally to RP structures in other perovskite systems.
钙钛矿半导体CsPbI因其合适的带隙在太阳能电池应用方面具有巨大潜力。然而，制备具有高功率转换效率的相稳定CsPbI太阳能电池仍然是一个重大挑战。在包括CsPbI在内的一系列钙钛矿半导体中已发现Ruddlesden-Popper（RP）缺陷。然而，对于它们为何形成以及对稳定性和光物理性质的影响，人们了解有限。在此，在气相沉积的CsPbI薄膜中，随着Cs过量增加，RP缺陷的发生率升高，同时观察到其具有优异的结构稳定性但光物理性质较差。值得注意的是，通过电子显微镜发现，平面缺陷处的原子位置与自由表面的原子位置相当，揭示了它们在相稳定中的作用。密度泛函理论（DFT）计算表明，RP平面在电子方面是良性的，然而，在RP转折点处观察到的反位缺陷可能是有害的。因此，建议增加RP平面同时减少RP转折点为提高相稳定性和光物理性能提供了突破。这里揭示的形成机制可以更广泛地应用于其他钙钛矿体系中的RP结构。
