Sequential Crystallization during the Formation of Bulk Heterojunction in Organic Solar Cells

• • Sequential crystallization manipulation enabled a 20.82% PCE in organic solar cells with high tolerance of active layer thickness, as reported in Nat Mater 2025, 24: 444–453, directly addressing the thickness-PCE trade-off that limits scalable manufacturing. • • The active layer thickness in OSCs is typically ~100 nm; increasing thickness to reduce pinholes often causes PCE drop, but controlled crystallization sequence mitigates this, allowing thicker films without sacrificing performance. • • Exciton diffusion length is on the order of 10 nm, necessitating BHJ interpenetrating networks with domain sizes comparable to this length to ensure efficient exciton dissociation; sequential crystallization optimizes domain purity and alignment. • • The third-generation OSCs utilize materials with bandgaps of 1–4 eV and high absorption coefficients, but short exciton lifetimes and diffusion lengths require precise morphological control to achieve PCEs competitive with silicon (>25%) and thin-film (10–15%) technologies.