Single Source Precursor Chemical Vapor Decomposition Method to Fabricate Stable, Bright Emissive Aluminum Hydroxide Phosphors for UV‐Pumped White Light‐Emitting Devices

Abstract

Aluminum hydroxides are considered to be a potential abundant, low‐cost blue emissive material to construct UV‐pumped white light‐emitting diodes (WLEDs). In this work, a single‐source precursor chemical vapor decomposition method is adapted to fabricate stable, strongly emissive aluminum hydroxide phosphors with photoluminescence quantum yield of up to 69% in solid state by thermal decomposing aluminum diacetate hydroxide (Al(OH)(Ac)2) at temperatures (260–360 °C) in N2 atmosphere. It exhibits layered, amorphous structure and its emission of aluminum hydroxide is enhanced by electron‐donating surface hydroxyl groups and originates from F+ centers and carbon‐related defects contributing to UV (388 nm) and blue (450–520 nm) spectral regions, respectively. Employing the as‐fabricated aluminum hydroxides as blue phosphor and CuInS2 nanocrystals as red phosphor, high color rendering and high‐efficiency WLEDs with luminous efficiencies up to 37 lm W−1 and high color rendering index of 91 are fabricated. This is the best performance reported so far for aluminum hydroxide based LEDs.

Synthesis of UV/blue light-emitting aluminum hydroxide with oxygen vacancy and their application to electrically driven light-emitting diodes

“…12,14,16,18 It is important to investigate those optical phenomena in order to widen its applications to optical sensors, LEDs, waste treatment, medical science, etc. 3,4,6,9,13–20 As demonstrated in previous works, aluminum hydroxide nanomaterials emit UVA light (383–400 nm) due to their oxygen vacancy (F + center, i.e. , one electron trapped at an anion vacancy) and blue light (450–470 nm) caused by carbon related radical impurities on the surface from the decomposition of metal–organic precursor or organic compound such as aluminum diacetate hydroxide, aluminum triacetate, benzoyl alcohol, oxalic acid, etc.…”

“…one electron trapped at an oxygen vacancy) and carbonyl radical causing UV and blue light are located within the wide band gap of aluminum hydroxide. 4,12,14,16–18,29–33 Additional PLE spectra of Sample-A and B monitored at 390 nm wavelength are in Fig. S1(a) and (b) †.…”

“…, one electron trapped at an anion vacancy) and blue light (450–470 nm) caused by carbon related radical impurities on the surface from the decomposition of metal–organic precursor or organic compound such as aluminum diacetate hydroxide, aluminum triacetate, benzoyl alcohol, oxalic acid, etc. 13–21 Additionally, the faintly green light emission (500–550 nm) is presented owing to the hydroxyl group and carbon compounds (such as Al–OH, CO 2 , 1,2,3,4-tetrahydrocarbazole, etc. ) on the surface of aluminum hydroxide particles.…”

“…12,14,16,18 Recently, aluminum hydroxide materials that emit UV and blue light with photoluminescence quantum yields (PLQYs) 38–65% with ∼100 nm of the full width at half maximum (FWHM) have been made in various forms such as nanoplates, rods, fibers, wires, and particles by using CVD, pulsed laser ablation (PLA), and a sol–gel method at harsh conditions of 320 °C or higher with a long synthesis duration of 20–72 hours. 4,12,14,16–18 Due to their optical properties, emissive aluminum hydroxide have been applied to solar photovoltaics by combining with polymers to form a polymeric composite luminescent film, and to UV-pumped white LEDs (which use UV-LED chips emitted at 370–407 nm of wavelength) with a color rendering index (CRI) value of 94. 12,16–18 So, a straightforward synthetic method and application to UV–blue light-emitting diodes are highly needed.…”

“…4,12,14,16–18 Due to their optical properties, emissive aluminum hydroxide have been applied to solar photovoltaics by combining with polymers to form a polymeric composite luminescent film, and to UV-pumped white LEDs (which use UV-LED chips emitted at 370–407 nm of wavelength) with a color rendering index (CRI) value of 94. 12,16–18 So, a straightforward synthetic method and application to UV–blue light-emitting diodes are highly needed. In this study, amorphous aluminum hydroxide nanoparticles (Al(OH) 3− x ) with oxygen defect and carbonyl radical on the surface were rapidly obtained by the simple synthetic method at a low temperature of 200 °C for 10 minutes using a base catalyst.…”