Increasing the Power: Absorption Bleach, Thermal Quenching, and Auger Quenching of the Red‐Emitting Phosphor K2TiF6:Mn4

• Published in: Advanced optical materials 2023-05, Vol.11 (9), p.n/a
• Main Authors: Wit, Jur W., Swieten, Thomas P., Haar, Marie Anne, Meijerink, Andries, Rabouw, Freddy T.
• Format: Article
• Language: English
• Subjects: Absorption; absorption bleach; Auger quenching; Augers; Bleaches; droop; Fluorides; Light emitting diodes; Materials science; Optics; Phosphors; Quenching; red phosphor; thermal quenching
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202202974

Mn4+‐doped fluorides are popular phosphors for warm‐white lighting, converting blue light from light‐emitting diodes (LEDs) into red light. However, they suffer from droop, that is, decreasing performance at increasing power, limiting their applicability for high‐power applications. Previous studies highlight different causes of droop. Here, a unified picture of droop of Mn4+‐doped K2TiF6, accounting for all previously proposed mechanisms, is provided. Combining continuous‐wave and pulsed experiments on samples of different Mn4+ content with kinetic Monte Carlo modeling, the contributions of absorption bleach, thermal quenching, and Auger quenching at different excitation densities, are quantified. This work contributes to understanding the fundamental limitations of these materials and may inspire strategies to make Mn4+‐doped fluorides more efficient in high‐power applications. The droop behavior of K2TiF6:x% Mn4+ (x = 0.1, 0.8, 1.3, and 5.4) is explained using a combination of experiments and simulations. High excitation powers create a high Mn4+ excited‐state population. The phosphor then suffers from absorption bleach, Auger quenching, and thermal quenching. These effects can be partially remedied by operating the phosphor just below the thermal‐quenching temperature.