Synthesis and optical properties of lead-free white-light-emitting single-phase complexes

Abstract

Lead-free halide perovskites have emerged as promising optoelectronic materials owing to their non-toxic composition, structural adaptability, and exceptional photophysical characteristics. In this work, novel lead-free KZnF₃: Eu³⁺, Tb³⁺/OA complexes were synthesized through introducing oleic acid (OA) during the solvothermal synthesis of the KZnF₃: Eu³⁺, Tb³⁺ perovskite. This synthetic strategy induces the formation of Tb–O coordination bonds, significantly enhancing the broadband blue emission (425–525 nm) with a dominant peak at 495 nm in the photoluminescence (PL) spectra. The synthesized KZnF₃: Eu³⁺, Tb³⁺/OA complexes exhibit characteristic blue, green, and red emission peaks of Tb³⁺ and Eu³⁺ ions upon excitation at 375 nm, thereby achieving a lead-free single-phase white light material through ultraviolet (UV) excitation. Additionally, these complexes demonstrate excellent thermal stability, retaining approximately 60% (495 nm), 70% (545 nm), and 90% (594 nm) of their relative PL intensities at 120 °C compared to those at 40 °C. The calculated lifetime of the complexes is 18.33 μs. Finally, the white-emitting KZnF₃: Eu³⁺, Tb³⁺/OA complexes are encapsulated on an ultraviolet (UV)-emitting chip to fabricate a white light-emitting diode (WLED) with the Commission International de L'Eclairage (CIE) color coordinates at (0.336, 0.333), approaching ideal white-light emission.