Crystal facet engineering in perovskite photovoltaics: the rise of (111)-oriented structures

Perovskite solar cells (PSCs) are regarded as a promising candidate for next-generation photovoltaics. Facet engineering for the controlled growth of perovskite crystals has emerged as a breakthrough strategy to address the efficiency-stability trade-off in PSC devices. Among various crystallographic orientations, (111)-oriented perovskite films have garnered significant attention due to their unique advantages in defect tolerance, ion migration suppression, and environmental adaptability. This review systematically summarizes the structural, electronic, and stability characteristics of the (111) facet. By analyzing key engineering strategies such as additive-regulated growth, ligand-assisted crystallization, and substrate-template induction, the roles of these methods in suppressing competitive facet orientations and promoting preferential (111) alignment are revealed. Experimental evidence demonstrates that (111)-dominated orientations exhibit superior stability in perovskite films across different bandgaps, making them ideal for both single-junction perovskites and tandem devices. Despite notable progress, challenges remain in scaling up (111)-predominant films with homogeneous morphology and reconciling growth kinetics with thermodynamic stability. Emerging solutions, such as machine learning-guided additive design and in situ characterization of facet-dependent degradation, are highlighted as critical pathways to unlock commercial viability. By bridging fundamental crystallography and device performance, this review provides a roadmap for leveraging (111) facet engineering to unleash the full potential of PSCs.