Broadening Phosphor-Converted Light-Emitting Diode Emission: Controlling Disorder
Chih‐Yu Chang, Natalia Majewska, Kuan‐Chun Chen, Wen‐Tse Huang, Tadeusz Leśniewski, Grzegorz Leniec, S.M. Kaczmarek, Wei Kong Pang, Vanessa K. Peterson, Ding‐Hua Cherng, Kuang‐Mao Lu, Sebastian Mahlik, Ru‐Shi Liu
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.