Structural evolution of organic-inorganic hybrid crystals for high colour-rendering white LEDs.

Luminescent crystals with high efficiency have huge potential in applications for white light-emitting diodes (LEDs). Herein, organic-inorganic hybrid crystals doped with Mn 4+ , [N(CH 3 ) 4 ] 2 XF 6 :Mn 4+ (X = Si, Ge, and Ti), were grown under mild conditions. Their crystal structural evolution was confirmed by single-crystal X-ray diffraction at different temperatures. These crystals exhibit intense red emission with a high external quantum efficiency (73.0% for [N(CH 3 ) 4 ] 2 TiF 6 :Mn 4+ ) and good thermal stability. The warm white LEDs were fabricated by combining these red-emitting phosphors with a YAG:Ce 3+ ceramic chip. As-grown crystals can significantly optimize the performances of white LEDs (colour rendering index up to 95). Hence, this work provides a new strategy to explore Mn 4+ -activated organic-inorganic hybrid materials for white LEDs.