Direct measurement of the triplet exciton diffusion length in organic semiconductors
article
We present a new method to measure the triplet exciton diffusion length in organic semiconductors. N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-biphenyl)-4,4′-diamine (NPD) has been used as a model system. Triplet excitons are injected into a thin film of NPD by a phosphorescent thin film, which is optically excited and forms a sharp interface with the NPD layer. The penetration profile of the triplet excitons density is recorded by measuring the emission intensity of another phosphorescent material (detector), which is doped into the NPD film at variable distances from the injecting interface. From the obtained triplet penetration profile we extracted a triplet exciton diffusion length of 87±2.7nm. For excitation power densities >1mW/mm2 triplet-triplet annihilation processes can significantly limit the triplet penetration depth into organic semiconductor. The proposed sample structure can be further used to study excitonic spin degree of freedom. © 2012 American Physical Society.
Topics
Direct measurementEmission intensityExcitation power densityModel systemPenetration profilesPhosphorescent materialSample structureSharp interfaceSpin degreesTriplet excitonsTriplet-triplet annihilationDiffusionInterfaces (materials)NaphthalenePhosphorescenceProduct developmentSemiconducting organic compoundsThin filmsExcitons
TNO Identifier
461328
ISSN
00319007
Source
Physical Review Letters, 108(13)
Article nr.
137401
Collation
5 p.
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