Dynamic assembly stabilizes buried 2D perovskite
Perovskite solar cells (PSCs) are leading candidates in third-generation photovoltaics, yet achieving uniform crystallization from top to buried interfaces remains critical for high efficiency and stability. The buried interface is particularly challenging due to substrate-induced nucleation suppression and spatial confinement, leading to disordered crystallization, small grains, and high defect densities. Residual strain from thermal expansion mismatch further exacerbates defect formation and non-radiative recombination. Existing strategies, such as heterogeneous nucleation sites or pre-deposited 2D perovskite seeds, often fail because these layers are washed away or dissolved during subsequent processing, compromising structural integrity and reproducibility. In a recent breakthrough, Chen et al. (2025) reported the construction of stable buried 2D perovskites using specially designed organic spacer cations: 2,3-dihydroisoindole hydroiodide (DHIII) and 4,5,6,7-tetrahydrothieno[3,2-c]pyridine hydroiodide (ThPyI). Unlike conventional spacers like phenethylammonium (PEA) and 2-thiophenemethylammonium (ThMA), DHIII and ThPyI induce spontaneous formation of 2D perovskites that remain stable during subsequent spin-coating and annealing. This buried 2D structure effectively templates the growth of high-quality 3D perovskites, improving crystallization uniformity and passivating defects. The work demonstrates a viable route to overcome the long-standing challenge of stabilizing 2D phases at the buried interface, potentially enabling more efficient and stable PSCs.