Bismuth activated blue phosphor with high absorption efficiency for white LEDs

Abstract

Trivalent bismuth (Bi3+) activated blue-emitting materials have attracted considerable attention because they effectively avoid the reabsorption demerits compared to traditional rare earth activators. Unfortunately, these materials are often plagued by mismatch to the near-ultraviolet (n-UV) chip and short blue emission peak as well as low n-UV absorption efficiency. In this work, we successfully designed a blue-emitting phosphor SrZnSO:Bi3+ with a wide n-UV excitation band ranging from 310 to 400 nm and an ideal blue emission band centered at 460 nm. Furthermore, SrZnSO:0.03Bi3+ phosphor exhibits an extraordinary absorption efficiency of 73.21% ascribed to the intense absorption of the matrix and Bi3+ in the n-UV region. The relationship between the excitation peak position of Bi3+-related phosphors and the size of the polyhedron were also summarized. A white light-emitting diode (WLED) was fabricated using a 370 nm n-UV chip, the composition-optimized sample SrZnSO:0.03Bi3+ and the commercial phosphors. Interestingly, the temperature-sensitive luminescence behavior is beneficial to the performance improvement of the WLED. The WLED demonstrates a warm white light whose Commission Internationale de L′Eclairage (CIE) coordinates are (0.3817, 0.3885), outstanding color rendering index of 93.4 and low correlated color temperature of 4051 K at current of 80 mA. The study suggests that SrZnSO:Bi3+ blue emitting phosphor has great potential in LED-based applications. Also inspires researchers to explore Bi3+-related phosphors with low energy excitation band and high absorption efficiency to develop high-quality n-UV pumped WLEDs.