Accelerated Screening of Dimension-Controlled Cu3– y A y VS4– x Se x (A = K, Rb, Cs) via Soft Chemistry

Dimension-driven design offers a powerful strategy for tuning the electronic structure of multinary chalcogenides, yet its application to solar absorbers remains limited. Previously explored systems lack candidates with optimal band gaps, while the time-consuming nature of solid-state synthesis impedes rapid synthesis and characterization of high-purity materials. Here, we report a colloidal soft-chemistry approach to systematically explore the Cu3–yAyVS4–xSex (A = K, Rb, Cs; y = 0, 1, 2; 0 ≤ x ≤ 3.5) compositional space, enabling simultaneous control over structural dimensionality (y), alkali-metal composition (A+), and chalcogen ratio (x) within a unified synthetic framework. By varying only precursor ratios, we access a broad family of phases spanning three-dimensional (3D), two-dimensional (2D), and one-dimensional (1D) [Cu–V–S] frameworks, as well as highly complex septenary solid solutions such as Cu(K, Rb, Cs)2VS2Se2. The resulting materials exhibit x-, y-, and A+-dependent optoelectronic properties, with band gaps tunable within the solar-relevant range of 1.40–1.67 eV, favorable band-edge alignment with CdS buffer layers, and intrinsic photocurrent responses. Theoretical calculations further elucidate the energy landscape and band structures of the understudied 1D series. Temperature- and time-resolved aliquot studies reveal pathway-dependent formation mechanisms, including direct nucleation of sulvanite Cu3VS4 and a two-step alkali-metal incorporation process governing the formation of alkali-metal-containing structures, providing key insights for related multinary chalcogenide systems. Overall, this work establishes a versatile platform for efficiently screening composition–structure–property relationships in complex chalcogenides for optoelectronic applications.