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

Abstract

Near-infrared (NIR) phosphor-converted light-emitting 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 Ga3+ with (Al0.68In0.32)3+, we create a Ga2–x(Al0.68In0.32)xO3:Cr3+ 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.