Cluster-Centered Excited-State-Induced Bright Low-Energy Emissive Hybrid Copper Iodide Constructing Stable White LEDs

Abstract

Herein, we successfully synthesized a stable copper iodide hybrid with a 0D structure, (C₂₀H₂₀P)₂Cu₂I₄, in which [Cu₂I₄]^2- dimers with a short Cu-Cu distance (2.64 Å) are isolated and surrounded by [C₂₀H₂₀P]⁺ organic cations. Bright broadband yellow emission (576 nm) featuring a wide excitation range from 240 to 450 nm was achieved, along with a large Stokes shift (211 nm), long-lived lifetime (1.99 μs), and zero self-absorption. The results combined with crystal structure, spectroscopy analysis, and theoretical studies reveal that a cluster-centered excited state is responsible for this yellow emission. Importantly, the structure of (C₂₀H₂₀P)₂Cu₂I₄ remains unchanged even after soaking in water for 30 days or heating at 80 °C for 240 h due to the intermolecular interaction. Furthermore, a stable white LED showing a naturally correlated color temperature (CCT) of 6573 K and CIE color coordinate of (0.31, 0.37) was also demonstrated. This work demonstrates efficient light emitters based on lead-free and stable metal halides for lighting, providing an important reference for the development of stable, high-performance metal halide phosphors.