New-Type Stable Double Perovskite Cs3CuAgI5 Single Crystal with Self-Trapping Exciton Emission for Optoelectronics

After replacement of Pb2+ by monovalent cations and trivalent cations in traditional double perovskites, the cubic unit cell formed in the crystal structure restricts the interaction between adjacent cation orbitals. Herein, we first design and synthesized a new-type lead-free double perovskite Cs3CuAgI5 single crystal (SC) by antisolvent method. The Cs3CuAgI5 single crystal exhibits direct band gap at the G point with a band gap of 2.63 eV and the differential charge density display structure is 0D. Furthermore, the Cs3CuAgI5 perovskite exhibited an emission peak of 460 nm, a Stokes-Shift of 160 nm, a long fluorescence lifetime of 8.15 μs, and superior stability of photoluminescence (PL) intensity maintained at about 90% after 90 days and demonstrated excellent thermal stability. Additionally, a white-light emitting device was produced using the Cs3CuAgI5 single crystal, showcasing outstanding white-light emission with a high color rendering index (CRI) of 87.5, a correlated color temperature (CCT) of 4879 K, and remarkable stability, even at elevated temperatures of up to 100 °C.