Enhanced Photoluminescence Quantum Efficiency of Cs 3 Cu 2 I 5 by Modulating the Superposition of Exciton Wavefunctions

Abstract

Although Pb-based halide perovskites exhibit excellent performance in light-emitting diode applications, its practical application is limited because Pb is a heavy metal with toxicity and poses serious risks to human health and the environment. Numerous studies have substituted Pb with other elements, such as Sn, Sb, and Bi; however, these materials cannot achieve the desired levels of emission performance and stability. Among them, Cu halide perovskites can potentially address these limitations. Cs 3 Cu 2 I 5 exhibits an octahedral structure and benefits from a strong Jahn-Teller effect and minimal spatial expansion of the wave function, facilitating effective exciton confinement. In this study, a new strategy to further increase the quantum efficiency and stability of Cu halide perovskites is proposed. After introducing tetrabutylammonium (TBA) into Cs 3 Cu 2 I 5 , the crystal grain size can be modulated, enhancing the photoluminescence quantum yield up to ~89%. Notably, this value is among the highest reported for Cs 3 Cu 2 I 5 perovskites. The rearrangement of TBA dopant molecules on the surface of the Cs 3 Cu 2 I 5 crystals contributes to improved air stability, and scintillator properties under X-ray radiation illumination are demonstrated using TBA-doped Cs 3 Cu 2 I 5 . This study demonstrates that the proposed organic ion introduced strategy on 0D Cs 3 Cu 2 I 5 scintillation films can improve luminescence properties.