Naphthyl-modified graphitic carbon nitride: Preparation and application in light-emitting diodes

Abstract

A series of naphthyl-modified graphitic carbon nitride were prepared by using melamine, cyanuric acid as precursors and 6-(naphthalen-2-yl)-1,3,5-triazine-2,4-diamine as a molecular dopant. When their mass ratio was 20:20:1, the product (g–C3N4–Naphth20:20:1) showed the best photoluminescence performances. The emission spectrum of g–C3N4–Naphth20:20:1 was mainly at 410–650 nm and much wider than that of bulk g-C3N4 (mainly at 410–550 nm), relative to bulk g-C3N4, the maximum emission wavelength (λem,max) changed from 455 nm to 485 nm, the light color correspondingly changed from deep blue to blue-green, the PL efficiency increased from 5.1% to 11.3%. Excited by ultraviolet chips (λem,max = 365 nm), a series of LEDs using g–C3N4–Naphth20:20:1 blended in epoxy resin at 4.0 wt% together with red-emitting SrAlSiN3:Eu2+ at x wt-% (x = 0.08, 0.12, 0.16, and 0.20) as phosphors were fabricated. When x = 0.08, 0.12, 0.16, the LEDs emitted neutral white light, their correlate color temperatures (CCT) were 5277 K, 4602 K and 3794 K, color rendering indexes (CRI) were 85.4, 88.1 and 79.7, respectively. When x = 0.20, it was a warm white LED, its CCT was 3312 K and CRI was 83.3. The results suggested the naphthyl-modified g-C3N4 can be used as efficient metal-free phosphors for LEDs.