Tuning the diurnal natural daylight with phosphor converted white LED–Advent of new phosphor blend composition

Abstract

We demonstrate the feasibility of developing phosphor converted white LED (pc-WLED) that mimics diurnal natural daylight with the newly designed phosphor blend in the color temperature (CCT) 2700-6000 K for health benefits. Natural daylight (sunlight) spectrum possesses broad emission in the visible region and closely approximates black body radiator, with color rendition index (CRI) of 100 under wide CCT (2500-6500 K). Current white light LEDs although are efficient and durable, they are not broad enough compared to daylight. We report new phosphor blend based on Sr3MgSi2O8:Eu2+ blue phosphor with broad emission and high CRI >= 96 under both near UV and blue excitation. The fabricated WLED has exhibited similar to 91% spectral resemblance with natural daylight compared to 39.2% for YAG:Ce3+ white LED at 4500 K. The developed phosphor blend tunes the spectrum in wider CCT and would be a prospective candidate for full spectrum daylight WLED.