Broadening Phosphor-Converted Light-Emitting Diode Emission: Controlling Disorder

Abstract

Near-infrared (NIR) phosphor-converted lightemitting diodes (pc-LEDs) are a highly efficient perspective NIR light source, with application hindered by a narrow emission band. In this work, we broaden the emission of a new series of NIR phosphors by controlling crystal structure disorder through cation cosubstitution. By substituting Ga 3+ with (Al 0.68 In 0.32 ) 3+ , we create a Ga 2−x (Al 0.68 In 0.32 ) x O 3 :Cr 3+ phosphor series in which the average crystal size is maintained, while cation disorder varies. The increased deviation of the cation radii in the substitution leads to increased electron−phonon coupling, with a resulting emission spectrum covering the 650−1000 nm range with a 30% increase in the emission full width at half-maximum (FWHM) and a relatively high internal quantum efficiency of ∼80%. A transition from the β phase to the α phase, which differs in structure from the undoped parent, is created by the application of high pressure and possesses ultra-broad-band emission and an FWHM of ∼190 nm. This work shows that the emission bandwidth can be controlled through disorder and its influence on the Stokes shift, as captured by the effective Huang−Rhys factor.

An efficient and thermally stable near-infrared phosphor derived from the Ln3ScInGa3O12:Cr3+ (Ln = La, Gd, Y, and Lu) garnet family

“…The spectral broadening is mainly related to the enhancement of electron–lattice coupling caused by a slight but non-negligible local structural distortion when the smaller Cr 3+ ions substitute the larger Sc 3+ or In 3+ ions. 48 The optimal Cr 3+ doping concentration is x = 0.06 based on the emission intensity, beyond which the concentration quenching effect will happen.…”

Ultra-broadening near-infrared emission of Cr3+-activated pyroxene phosphors via chemical unit substitution and Yb3+ co-doping

“…Regarding the elemental disorder existing in the (Ca 1− x Li x )(Mg 1− x Sc x )Si 2 O 6 ( x ≠ 0 and 1) solid solution, Cr 3+ ions tend to emit photons in a wider energy distribution. Chang et al suggested a parameter ( σ ) to quantify the disorder degree in a solid-solution system, using the following equation: 24 where N is the total number of elements, x i is the radius of particular elements i , and is the average radius of the system. From Fig.…”

High Output Power and High Quantum Efficiency in Novel NIR Phosphor MgAlGa0.7B0.3O4:Cr3+ with Profound FWHM Variation

“…As shown in Figure 3c, the peaks at 713, 748, and 895 nm are clearly distinguishable, and the narrow line at 713 is the R line assigned to the 2 E→ 4 A 2g transition of the Cr 3+ ions. [15] The peaks at 748 and 895 nm are attributed to the two different 4 T 2g → 4 A 2g transitions of the Cr 3+ ions, which implies that there are three emission centers in the sample. Time-resolved photoluminescence spectra were measured at 7 K and are plotted in Figure 3d to further study the luminescence centers.…”