Browsing by Author "Yu, Holly A."

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A red-orange carbazole-based iridium(III) complex: Synthesis, thermal, optical and electrochemical properties and OLED application
(Elsevier Science, 2021-07-21) Altınölçek, Nuray; Battal, Ahmet; Tavaslı, Mustafa; Cameron, Joseph; Peveler, William J.; Yu, Holly A.; Skabara, Peter J.; Fairbairn, Nicola J.; Hedley, Gordon J.; ALTINÖLÇEK GÜLTEKİN, NURAY; TAVASLI, MUSTAFA; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-9466-1111; JCN-8292-2023; AAB-1630-2020
A novel heteroleptic iridium(III) acetylacetonate (acac) complex, (L-5-CHO)(2)Ir(acac) (3b), was synthesised from 2-(9'-hexylcarbazole-3'-yl)-5-formylpyridine (L-5-CHO) (1b). The complex 3b was determined to be thermally and electrochemically stable. The photoluminescence properties of the compound were studied, with a dichloromethane solution of 3b giving structureless emission at 662 nm, showing that the formyl group red-shifted the emission by 151 nm compared to the parent complex. Complex 3b was also shown to possess a moderate photoluminescence quantum yield (67%) and a short emission lifetime (tau = 280 ns). Organic light-emitting diodes (OLEDs) were fabricated with a solution-processed emissive layer (EML) consisting of poly(N-vinylcarbazole) (PVK), 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PBD) and iridium complex (3b). The OLEDs containing complex 3b showed red-orange electroluminescence (EL) at 624 nm. The influence of the host materials was studied and the best performance was achieved with both PVK and PBD in the emissive layer, with the resulting OLEDs exhibiting a current efficiency of 0.84 cd/A, a power efficiency of 0.20 lm/W, and an external quantum efficiency (EQE) of 0.66% at a brightness of 2548 cd/m(2).
Carbazole-based D-π-A molecules: Determining the photophysical properties and comparing ICT effects of π-spacer and acceptor groups
(Elsevier, 2021-04-11) Altınölçek, Nuray; Battal, Ahmet; Vardallı, Cemre Nur; Tavaslı, Mustafa; Yu, Holly A.; Peveler, William J.; Skabara, Peter J.; ALTINÖLÇEK GÜLTEKİN, NURAY; Vardalli, Cemre Nur; TAVASLI, MUSTAFA; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-9466-1111; JCN-8292-2023 ; EDG-8300-2022 ; AAB-1630-2020
4-(9'-Hexylcarbazol-3'-yl)benzaldehyde (Cz-Ph-CHO: 4 ) and 4-(9'-hexylcarbazol-3'- yl)benzylidenemalononitrile (Cz-Ph-CN: 5 ) were synthesised with the structure of D-pi-A,where carbazole, phenylene and formyl/dicyanovinyl groups act as electron donor (D), pi-spacer (pi) and electron acceptor (A) units, respectively. The thermal, electrochemical, optical and intramolecular charge transfer (ICT) properties of compounds 4 and 5 were investigated. Compounds 4 and 5 , in particular their ICT behaviour, were also compared with the closely related structure, 2-(9'-hexylcarbazol-3'-yl)-5-pyridinecarbaldehyde (Cz-Py-CHO: 7 ). For the purpose of tuning chemical structure to obtain targeted properties, electrochemical data and absorption and emission measurements suggest that the dicyanovinyl unit in compound 5 is a better acceptor than formyl in compound 4, and that pyridine in compound 7 is a better pi-spacer than benzene in compound 4 , in exerting ICT characteristics such as fluorosolvatochromism and Stokes shifts.
Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties
(Beilstein-Institut, 2020-05) Battal, Ahmet; Peveler, William J.; Yu, Holly A.; Skabara, Peter J.; Altınölçek, Nuray; Tavaslı, Mustafa; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-9466-1111; JCN-8292-2023; AAB-1630-2020; 56955836600; 6506308760
Two novel carbazole-based compounds 7a and 7b were synthesised as potential candidates for application in organic electronics. The materials were fully characterised by NMR spectroscopy, mass spectrometry, FTIR, thermogravimetric analysis, differential scanning calorimetry, cyclic voltammetry, and absorption and emission spectroscopy. Compounds 7a and 7b, both of which were amorphous solids, were stable up to 291 degrees C and 307 degrees C, respectively. Compounds 7a and 7b show three distinctive absorption bands: high and mid energy bands due to locally excited (LE) transitions and low energy bands due to intramolecular charge transfer (ICT) transitions. In dichloromethane solutions compounds 7a and 7b gave emission maxima at 561 nm and 482 nm with quantum efficiencies of 5.4% and 97.4% +/- 10%, respectively. At positive potential, compounds 7a and 7b gave two different oxidation peaks, respectively: quasi-reversible at 0.55 V and 0.71 V, and reversible at 0.84 V and 0.99 V. At negative potentials, compounds 7a and 7b only exhibited an irreversible reduction peak at -1.86 V and -1.93 V, respectively.
Yellowish-orange and red emitting quinoline-based iridium(III) complexes: Synthesis, thermal, optical and electrochemical properties and OLED application
(Elsevier Science, 2020-07-06) Battal, Ahmet; Cameron, Joseph; Peveler, William J.; Yu, Holly A.; Skabara, Peter J.; Altınölçek, Nuray; Tavaşlı, Mustafa; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Kimya Bölümü.; 0000-0002-9466-1111; CCY-8756-2022; 56955836600; 6506308760
Two novel heteroleptic iridium(III) acetylacetonate (acac) complexes K3a and K3b were synthesised from cyclometallating ligands of 2-(4'-formylphenyl)quinoline lla and 2-(5'-formylphenyl)quinoline 11b. Complexes K3a and K3b were fully characterised by NMR spectroscopy, mass spectrometry and FT-IR. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) indicate that both complexes were amorphous solids, stable up to 303 degrees C and 313 degrees C, respectively. Complexes K3a and K3b showed strong, high-energy absorption bands ( <400 nm) due to ligand-centred ((LC)-L-1) transitions and weaker, low-energy absorption bands (400 - 600 nm) arising from a mixture of metal-to-ligand charge transfer ((MLCT)-M-1/(MLCT)-M-3) and ligand-centred ((LC)-L-3) transitions. In degassed dichloromethane solutions, complexes K3a and K3b gave yellowish-orange and red phosphorescent emissions at 579 nm and 630 nm, with quantum efficiencies of 99.3 % and 79.3 %, respectively. At positive potential, complexes K3a and K3b exhibited a one-electron reversible oxidation (En) peak at 0.69 V and a quasi-reversible oxidation (ET1/2ox) peak at 0.60 V, respectively, which were assigned to the Ir (III)/Ir(IV) couple. At negative potentials, complexes K3a and K3b exhibited a one-electron irreversible reduction peak at -1.79 V and -1.94 V, respectively. Phosphorescent organic light-emitting diodes (PhOLEDs) were fabricated with a device configuration of ITO/PEDOT:PSS/EML/TPBi/LiF/Al, in which K3a and K3b gave yellowish-orange and red electroluminescence (EL) at 572 nm and 628 nm, respectively. Complex K3a gave the highest luminance of 2773 cd/m(2), current efficiency of 3.3 cd/A, external quantum efficiency of 1.2 % and maximum power efficiency of 1.05 lm/W with a turn-on voltage of 5.0 V (Device A).