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Vapor-Deposited Organic Light-Emitting Devices
Published in Zhigang Rick Li, Organic Light-Emitting Materials and Devices, 2017
In a PHOLED system, all the singlet excited state (S1) excitons may be converted into the triplet excited state (T1) through intersystem crossing (S1 to T1) via the presence of a heavy metal atom. In these devices, the triplet states can decay to the singlet ground state (T1 to S0) and emit radiatively, enabling record high conversion efficiencies. The first generation of PHOLEDs contained platinum 2,3,7,8,12,13,17,18-octaethyl-12H,23H-porphyrin (PtOEP) as the phosphor [99] (see Figure 7.9). Porphine complexes possess long-lived triplet states that have been used in oxygen detection. This lifetime is reduced by addition of a platinum atom to the porphine ring due to the increased spin–orbit coupling. The result is an enhancement in efficiency due to the combined effect of forming 75% of the excitons directly as triplets in addition to the 25% that intersystem cross from the singlet excited state to the triplet excited state. The first published PtOEP devices had an external quantum efficiency of 4%. This was subsequently increased to 6% with the introduction of a blocking layer within the device structure [101]. Although at the time, this was an impressive device efficiency, it could only be realized at low drive currents and luminance levels. At high luminance levels due to the long-lived nature of the triplet excitons in PtOEP (>10 μs), the available dopant sites in the device at low dopant concentrations become saturated, which results in a roll-off in efficiency with increased current.
Some novel manganese(III) porphyrins with catalytic properties
Published in Journal of Coordination Chemistry, 2018
For the synthesis of 5,10,15,20-tetra(4-hydroxy-3-methoxyphenyl) porphine [H2THMPP], Adler’s method had been used with some modifications [21] according to which 5.6 mL (0.08 mol) of freshly distilled pyrrole and 12.16 g (0.08 mol) of vanillin were added in 300 mL of boiling propionic acid. The reaction mixture was refluxed for 2 h and then cooled, followed by 12 h of refrigeration. The tarry reaction mixture was filtered and washed thoroughly with methanol until the filtrate became colorless. Shining purple crystals of porphyrin were obtained, dried in a vacuum desiccator and recrystallized with 1:1 ratio of chloroform and dichloromethane.
Mini review: Recent advances in long period fiber grating biological and chemical sensors
Published in Instrumentation Science & Technology, 2019
In 2016, this team prepared a multilayer film of polydiallyldimethyammonium chloride and tetrakis 4-sulfophenyl porphine.[88] The tetrakis 4-sulfophenyl porphine in the multilayer film acted as the receptor and reacted with ammonia. HCl vapor was used to enhance the surface activity of tetrakis 4-sulfophenyl porphine and improve the sensitivity. The results show that the device with tetrakis 4-sulfophenyl porphine as the receptor had higher sensitivity and a lower detection limit than previous sensors.