Articles written in Journal of Chemical Sciences
Volume 120 Issue 4 July 2008 pp 355-362
A new class of highly fluorescent 9,9'-
Volume 122 Issue 2 March 2010 pp 119-124 Full Papers
A series of 2,8-𝑝-diaryldibenzothiophene derivatives were synthesized and characterized. These molecules have electron withdrawing or electron donating groups at the
Volume 122 Issue 6 November 2010 pp 847-855 Full Papers
Synthesis, structure, optical absorption, emission and electroluminescence properties of a new blue emitting Al complex, namely,
Volume 128 Issue 9 September 2016 pp 1435-1443 Regular Article
Nucleophilic substitution on 3-bromo/3,5-dibromo-4,4'-difluoro-8-(aryl)-4-bora-3a,4a-diaza-sindacene (BODIPY), substituted with anisyl or thienyl at meso positions, with neat pyrrole afforded the mono and di-pyrrole substituted BODIPYs 1–4 in good yields. Large bathochromic shifts, upto ∼180 nm in absorption maxima (581–682 nm), and fluorescence maxima (606–695 nm) were observed for these BODIPYs. Absorption and fluorescence properties were studied in different solvents to compare the effect of mono and di substitution on BODIPY. The Lippert-Mataga equations were used which predict strong polarization of monosubstituted BODIPYs. Electrochemical studies were carried out to find the oxidation potential and HOMO energy levels were calculated. Theoretical studies of 1–4 provide the insight on the electron density distribution in 1–4. Theoretical and experimental photo-physical studies in different solvents were correlated to findthe substituent effects on BODIPY.
Volume 129 Issue 9 September 2017 pp 1391-1398 Regular Aricle
Five heteroleptic, cyclometalated (C∧N) Iridium(III) complexes of acetylacetone (acac) and 1-phenyl-isoquinoline (piq) derivatives, Ir(acac)(piq) ₂, Ir(acac)(2,4-difluoro-piq) ₂, Ir(acac)(4-trifluoromethylpiq) ₂, Ir(acac)(4-N,N-dimethyl-piq) ₂, Ir(acac)(4-acetyl-piq) ₂, were synthesized and characterized. The ((C∧N) ₂ Ir(acac) complexes in toluene showed phosphorescence (λmax = 598 nm to 658 nm) with quantum yields (0.1 to 0.32) and microsecond lifetimes (0.43 to 1.9 μs). The complexes were non-luminescent in thin films due to self-quenching but luminescent when lightly doped (5%) in a host organic material, 4,4' -Bis(Ncarbazolyl)- 1,1' -biphenyl (CBP). The HOMO levels determined using cyclic voltammetric oxidation potentials were in the range−5.48 to−5.80 eV. Electroluminescence properties and performance of the Ir complexes dopedin CBP (active layer) were studied in a multilayer (ITO/F4TCNQ/TPD/doped CBP/BCP/LiF/Al) organic light emitting device (OLED). The electroluminescense (EL) spectra of the device matched with the phosphorescent spectra of the Ir complexes. The turn-on voltage at ∼4.5 V, maximum brightness of 7600 cd/m² and current efficiency of ∼7.0 cd/A at a brightness of ∼100 cd/m² indicate that these are promising OLED materials.
Volume 130 Issue 12 December 2018 Article ID 0167
We report on the optimization of organic light emitting diode (OLED) devices using 1,8-di-(4-trifluromethylphenyl)-anthracene (CF3-DPA) as the active emissive layer. CF3-DPA emits in the deep blue region with an emission peak at 432 nm in solution which showed a slight red shift in thin films. CF3-DPA hashigh reported fluorescence quantum efficiency,~67%, as compared to 9,10-diphenyl anthracene (9,10-DPA).We optimized the OLED devices with different hole transporting layers (HTLs). Bilayer devices formed with N,N' -di(1-naphthyl)-N,N' -diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPD) as the HTL gave a reasonable light output. We observed that trilayer or multilayer devices with the inclusion of poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) and/or copper phthalocyanine as an additional HTL reduced the turn on voltage by ~5 to 9 V, though the brightness of the light emission also decreased. Including suitable carrier (electron or hole) transporting layers like 2, 2' ,2''' -(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi)and 4,4' -Bis(N-carbazolyl)-1,1' -biphenyl (CBP) increases the efficiency of the devices. From our studies, we conclude that though NPD/CF3-DPA interface is crucial for light emission, the performance of the devices is limited by the mismatch of the hole and electron mobilities and the low internal quantum efficiency of CF3-DPA in the solid state. Devices having ITO/NPD/CF3-DPA/TPBi/LiF-Al geometry were observed to be the most efficient.
Volume 131 Issue 9 September 2019 Article ID 0094
Acridone (acceptor) and naphthylamine (donor) based Donor-Acceptor-Donor (D-A-D) compound (1) was synthesised, characterised and its thermally-activated delayed fluorescence (TADF) properties were studied in detail. Compound 1 is fluorescent and emits in the green region (550 nm). The energy gapbetween the ground and the lowest excited singlet (S1) state is estimated to be 2.55 eV. The energy gap between the CT singlet and triplet states (ΔEST) was found to be ~0.3 eV. Small ΔES1-T1 is one of the important criteria for TADF to take place in a molecule and thus detailed photophysics has been studied.Transient lifetime measurements showed an increase in the fluorescence lifetime (s) on purging with N2, as compared with that in air-saturated solution, indicating the involvement of the triplet state in emission. Emission at 550 nm was also observed with a delay of 100 ls which corresponded to the delayed fluorescencein 1. The lifetime of TADF was found to be 176 ls. Applications of TADF materials in organic lightemitting devices (OLEDs) has gotten attention as TADF materials utilise the triplet excitons which helps in increasing internal quantum efficiency of device. Air-saturated based on 1 were fabricated and their intensity was found to be nearly as high as 17,000 Cd/m2 at 25 mA/cm2 which was comparable to many of the known TADF emitters.
Volume 134, 2022
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