What are the differences between organic and inorganic phosphor materials and advantage and limitation of them over each other.
Dear Ashish,
Complicated question, since it depends on the application you aim at! First of all I would subdivide phosphor materials into several classes, viz.
Organic low molecular weight materials
Polymers
(Metal organic) complexes
Cluster (Mo6 or W6 and so on)
Glasses
Quantum Dots
Inorganic nanoparticles
Inorganic microparticles
and single crystals.
The stability in general increases from top to the bottom since inorganic single crystals are very stable due to the high lattice energy (garnets, sesquioxides) causing a high melting point and the low surface area. Therefore, for my professional work I always used inorganic micorparticles or single crystals for fluorescent lamps, LEDs, lasers, emissive displays, or detectors, since lifetime is rather important, next to quantum yield and colour consistency.
However, if you aim at strong absorption organic compounds or QDots might be better due to the allowed and strong optical transitions. In OLED displays, most companies use Ir3+ complexes, since [Ir(ppy)3] and related compounds cover the whole visible spectrum (RGB) and they are rather stable due to the configuration [Xe]4f145d6 (low-spin) which yields the highest possible crystal-field stabilisation energy in an octahedral field. Thus it ís rather hard to find better coordination compounds.
The quantum yield depends on defect density, band gap, photoioinisation tendency, phonon spectrum, surface area, energy of the CT state and so on, while the surface is often a quenching site, due to surface terminating OH and COOH groups. Thus many people try to design core-shell particle to inactivate the surface w.rt. quenching. The attached lecture slides are useful to catch some more guesses....
All the best.
Thomas
Dear Ashish,
Complicated question, since it depends on the application you aim at! First of all I would subdivide phosphor materials into several classes, viz.
Organic low molecular weight materials
Polymers
(Metal organic) complexes
Cluster (Mo6 or W6 and so on)
Glasses
Quantum Dots
Inorganic nanoparticles
Inorganic microparticles
and single crystals.
The stability in general increases from top to the bottom since inorganic single crystals are very stable due to the high lattice energy (garnets, sesquioxides) causing a high melting point and the low surface area. Therefore, for my professional work I always used inorganic micorparticles or single crystals for fluorescent lamps, LEDs, lasers, emissive displays, or detectors, since lifetime is rather important, next to quantum yield and colour consistency.
However, if you aim at strong absorption organic compounds or QDots might be better due to the allowed and strong optical transitions. In OLED displays, most companies use Ir3+ complexes, since [Ir(ppy)3] and related compounds cover the whole visible spectrum (RGB) and they are rather stable due to the configuration [Xe]4f145d6 (low-spin) which yields the highest possible crystal-field stabilisation energy in an octahedral field. Thus it ís rather hard to find better coordination compounds.
The quantum yield depends on defect density, band gap, photoioinisation tendency, phonon spectrum, surface area, energy of the CT state and so on, while the surface is often a quenching site, due to surface terminating OH and COOH groups. Thus many people try to design core-shell particle to inactivate the surface w.rt. quenching. The attached lecture slides are useful to catch some more guesses....
All the best.
Thomas
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