Precision Synthesis of I–III–VI Ternary Semiconductor Nanoclusters via Self-Limiting Cation Exchange

Ternary I–III–VI semiconductors are important materials because of their environmental compatibility and broad tunability. However, achieving atomic-level control of multinary semiconductor materials remains a major challenge. Here, we report the precision synthesis of ternary nanoclusters with atomically defined stoichiometry, structure, and surface via self-limiting cation exchange. Specifically, the reaction between a Cu 26 Se 13 (PR 3 ) 14 template cluster and an InCl 3 –PR′ 3 complex produces a partially exchanged Cu 6 In 8 Se 13 Cl 4 (PR′ 3 ) 12 cluster in high purity and near-unity yield. The ternary cluster retains the icosahedral Se 13 anion framework, with In 3+ and Cu + cations self-assembled into a pseudo -core/shell heterostructure. All the phosphines bind to the outer-edge Cu +, while all the chlorides coordinate to the inner-facet In 3+ . The reaction is further generalized to Ga 3+, producing an analogous Cu 6 Ga 8 Se 13 Cl 4 (PR 3 ) 12 cluster. Such self-limiting cation exchange and precise assembly of multinary cations and ligands can be attributed to charge, coordination, steric, and symmetry factors. Theoretical calculations reveal that Cu + and In 3+ /Ga 3+ contribute significantly to the occupied and unoccupied frontier orbitals, respectively, leading to a broad absorption band with charge-transfer character. The clusters can be sintered to form bulk semiconductors with well-controlled stoichiometry, demonstrating their potential as precise precursors for solution processing of multinary semiconductors. We expect that atomically defined cation-exchange reactions will open opportunities for precision engineering of complex multinary semiconductor materials.