TY  - JOUR
A1  - Müller, Ulrich
A1  - Spenst, Peter
A1  - Kagerer, Philipp
A1  - Stolte, Matthias
A1  - Würthner, Frank
A1  - Pflaum, Jens
T1  - Photon‐Correlation Studies on Multichromophore Macrocycles of Perylene Dyes
JF  - Advanced Optical Materials
N2  - Organic dyes offer unique properties for their application as room temperature single photon emitters. By means of photon‐correlation, the emission characteristics of macrocyclic para‐xylylene linked perylene bisimide (PBI) trimers and tetramers dispersed in polymethyl methacrylate matrices are analyzed. The optical data indicate that, despite of the strong emission enhancement of PBI trimers and tetramers according to their larger number of chromophores, the photon‐correlation statistics still obeys that of single photon emitters. Moreover, driving PBI trimers and tetramers at higher excitation powers, saturated emission behavior for monomers is found while macrocycle emission is still far‐off saturation but shows enhanced fluctuations. This observation is attributed to fast singlet–singlet annihilation, i.e., faster than the radiative lifetime of the excited S1 state, and the enlarged number of conformational arrangements of multichromophores in the polymeric host. Finally, embedding trimeric PBI macrocycles in active organic light‐emitting diode matrices, electrically driven bright fluorescence together with an indication for antibunching at room temperature can be detected. This, so far, has only been observed for phosphorescent emitters that feature much longer lifetimes of the excited states and, thus, smaller radiative recombination rates. The results are discussed in the context of possible effects on the g(2) behavior of molecular emitters.
KW  - multichromophores
KW  - organic light emitting diodes
KW  - perylene dyes
KW  - photon‐correlation
KW  - single photon emission
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287219
VL  - 10
IS  - 14
ER  - 
TY  - JOUR
A1  - Bunzmann, Nikolai
A1  - Krugmann, Benjamin
A1  - Weissenseel, Sebastian
A1  - Kudriashova, Liudmila
A1  - Ivaniuk, Khrystyna
A1  - Stakhira, Pavlo
A1  - Cherpak, Vladyslav
A1  - Chapran, Marian
A1  - Grybauskaite‐Kaminskiene, Gintare
A1  - Grazulevicius, Juozas Vidas
A1  - Dyakonov, Vladimir
A1  - Sperlich, Andreas
T1  - Spin‐ and Voltage‐Dependent Emission from Intra‐ and Intermolecular TADF OLEDs
JF  - Advanced Electronic Materials
N2  - Organic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) utilize molecular systems with a small energy splitting between singlet and triplet states. This can either be realized in intramolecular charge transfer states of molecules with near‐orthogonal donor and acceptor moieties or in intermolecular exciplex states formed between a suitable combination of individual donor and acceptor materials. Here, 4,4′‐(9H,9′H‐[3,3′‐bicarbazole]‐9,9′‐diyl)bis(3‐(trifluoromethyl) benzonitrile) (pCNBCzoCF\(_{3}\)) is investigated, which shows intramolecular TADF but can also form exciplex states in combination with 4,4′,4′′‐tris[phenyl(m‐tolyl)amino]triphenylamine (m‐MTDATA). Orange emitting exciplex‐based OLEDs additionally generate a sky‐blue emission from the intramolecular emitter with an intensity that can be voltage‐controlled. Electroluminescence detected magnetic resonance (ELDMR) is applied to study the thermally activated spin‐dependent triplet to singlet up‐conversion in operating devices. Thereby, intermediate excited states involved in OLED operation can be investigated and the corresponding activation energy for both, intra‐ and intermolecular based TADF can be derived. Furthermore, a lower estimate is given for the extent of the triplet wavefunction to be ≥ 1.2 nm. Photoluminescence detected magnetic resonance (PLDMR) reveals the population of molecular triplets in optically excited thin films. Overall, the findings allow to draw a comprehensive picture of the spin‐dependent emission from intra‐ and intermolecular TADF OLEDs.
KW  - color tuning
KW  - exciplexes
KW  - organic light emitting diodes
KW  - spin
KW  - triplets
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224434
VL  - 7
IS  - 3
ER  -