Narrow-band red-emitting KZnF3:Mn4+ fluoroperovskites: insights into electronic/vibronic transition and thermal quenching behavior

Abstract

Mn⁴⁺ activated fluoride is known for its unique spectral features and low lost, meeting the urgent requirements for w-LED applications, especially in the field of wide-color-gamut backlights. Despite the ever-growing family, insightful investigations on the host-dependent electronic/vibronic transition and thermal quenching behavior of Mn⁴⁺ are insufficient. In this work, a new red-emitting KZnF₃:Mn⁴⁺ fluoroperovskite is synthesized via a facile co-precipitation method. Systematical studies are performed on its microstructure, electronic structure, and spectroscopic properties. By virtue of high-resolution spectroscopy down to 10 K, both the electronic/vibronic transitions for Mn⁴⁺ and [F₂⁻] defect centers are identified, the slight distortion of the [MnF₆]²⁻ octahedron deviating from O_h symmetry is disclosed, and multiple crystallographic site occupation of Mn⁴⁺ is demonstrated. Moreover, a comparative study on the thermal quenching behavior of different fluoride hosts with nominal O_h symmetry reveals its close dependence on the ⁴T_2g energy position in a configurational coordinate model and provides a rule of thumb to select an appropriate host with good thermal stability.