Synthesis and properties of naphthylamine derivative functionalized spiro-[fluorene-9,9′-xanthene] for single-component white light-emitting diodes

White light-emitting diodes (LEDs) with high color purity and color-rendering index have elicited much interest in many fields. In this work, a spiro-type molecule SFX-PNA was designed and synthesized by combining a spiro[fluorene-9,9′-xanthene] (SFX) core with naphthylamine derivative functionalized at the 2,3′,6′,7-positions. Studies revealed that the highly twisted configuration allowed SFX-PNA to exhibit good thermal stability and a broad blue-emissive band (λem = 466 nm) in the solid state. In combination with the intrinsic yellow luminescence (λem = 556 nm) of commercially available GaN ultraviolet LED chips, a white LED with SFX-PNA as the phosphor was successfully obtained, which showed high color purity with Commission Internationale de L'Éclairage coordinates of (0.30, 0.33) and a color-rendering index of 86.