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Fluorene Derivatives (fluorene + derivative)
Selected AbstractsInfluence of Molecular Weight on the Performance of Organic Solar Cells Based on a Fluorene DerivativeADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Christian Müller Abstract The performance of organic photovoltaic (OPV) bulk-heterojunction blends comprising a liquid-crystalline fluorene derivative and a small-molecular fullerene is found to increase asymptotically with the degree of polymerization of the former. Similar to various thermodynamic transition temperatures as well as the light absorbance of the fluorene moiety, the photocurrent extracted from OPV devices is found to strongly vary with increasing oligomer size up to a number average molecular weight, Mn,,,10,kg,mol,1, but is rendered less chain-length dependent for higher Mn as the fluorene derivative gradually adopts polymeric behavior. [source] Highly Efficient Non-Doped Blue Organic Light-Emitting Diodes Based on Fluorene Derivatives with High Thermal Stability,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2005L. Tao Abstract A new series of blue-light-emitting fluorene derivatives have been synthesized and characterized. The fluorene derivatives have high fluorescence yields, good thermal stability, and high glass-transition temperatures in the range 145,193,°C. Organic light-emitting diodes (OLEDs) fabricated using the fluorene derivatives as the host emitter show high efficiency (up to 5.3,cd,A,1 and 3.0,lm,W,1) and bright blue-light emission (Commission Internationale de L'Eclairage (CIE) coordinates of x,=,0.16, y,=,0.22). The performance of the non-doped fluorene-based devices is among the best fluorescent blue-light-emitting OLEDs. The good performance of the present blue OLEDs is considered to derive from: 1),appropriate energy levels of the fluorene derivatives for good carrier injection; 2),good carrier-transporting properties; and 3),high fluorescence efficiency of the fluorene derivatives. These merits are discussed in terms of the molecular structures. [source] Facile Synthesis of Polycyclic Fluorene Derivatives via a Palladium-Catalyzed Coupling, Propargyl-Allenyl Isomerization and Schmittel Cyclization SequenceADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Ruwei Shen Abstract A stepwise process involving Sonogashira coupling, propargyl-allenyl isomerization and Schmittel cyclization has been realized, leading to an efficient synthesis of polycyclic fluorene derivatives from readily available starting materials. The reaction features the formation of three new carbon-carbon bonds to construct the benzene unit together with an efficient assembly of three or four rings in a single operative step. [source] Photoluminescent Color and Polarized Light Emission Tuning of Fluorene Derivatives Using a Photoreactive H-Bonded Liquid Crystalline PolymerMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Nobuhiro Kawatsuki Abstract Three fluorene (FL) derivatives with pyridine end groups were synthesized to control the photoluminescence (PL) wavelength and polarized light emission using a photoreactive H-bonded polymer containing cinnamic acid side groups (P6CAM). The FL derivatives, which possessed pyridine end groups, formed H-bonds with cinnamic acid, and changed the PL behavior of the derivatives. The controllability ,max of the PL depended on the position of the N-atom at the pyridine end group and the degree of the photoreaction of the P6CAM. For F1, ,max of the PL was tuned from 470 to 518,nm. Employing P6CAM as the photoalignment layer to reorient the cinnamic acid side groups realized polarized PL up to PL||/PL,,=,3.9. Furthermore, photopatterning of the PL color and the direction of the polarized light emission using patterned P6CAM films were demonstrated. [source] Influence of Molecular Weight on the Performance of Organic Solar Cells Based on a Fluorene DerivativeADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Christian Müller Abstract The performance of organic photovoltaic (OPV) bulk-heterojunction blends comprising a liquid-crystalline fluorene derivative and a small-molecular fullerene is found to increase asymptotically with the degree of polymerization of the former. Similar to various thermodynamic transition temperatures as well as the light absorbance of the fluorene moiety, the photocurrent extracted from OPV devices is found to strongly vary with increasing oligomer size up to a number average molecular weight, Mn,,,10,kg,mol,1, but is rendered less chain-length dependent for higher Mn as the fluorene derivative gradually adopts polymeric behavior. [source] Highly Efficient Non-Doped Blue Organic Light-Emitting Diodes Based on Fluorene Derivatives with High Thermal Stability,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2005L. Tao Abstract A new series of blue-light-emitting fluorene derivatives have been synthesized and characterized. The fluorene derivatives have high fluorescence yields, good thermal stability, and high glass-transition temperatures in the range 145,193,°C. Organic light-emitting diodes (OLEDs) fabricated using the fluorene derivatives as the host emitter show high efficiency (up to 5.3,cd,A,1 and 3.0,lm,W,1) and bright blue-light emission (Commission Internationale de L'Eclairage (CIE) coordinates of x,=,0.16, y,=,0.22). The performance of the non-doped fluorene-based devices is among the best fluorescent blue-light-emitting OLEDs. The good performance of the present blue OLEDs is considered to derive from: 1),appropriate energy levels of the fluorene derivatives for good carrier injection; 2),good carrier-transporting properties; and 3),high fluorescence efficiency of the fluorene derivatives. These merits are discussed in terms of the molecular structures. [source] Facile Synthesis of Polycyclic Fluorene Derivatives via a Palladium-Catalyzed Coupling, Propargyl-Allenyl Isomerization and Schmittel Cyclization SequenceADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Ruwei Shen Abstract A stepwise process involving Sonogashira coupling, propargyl-allenyl isomerization and Schmittel cyclization has been realized, leading to an efficient synthesis of polycyclic fluorene derivatives from readily available starting materials. The reaction features the formation of three new carbon-carbon bonds to construct the benzene unit together with an efficient assembly of three or four rings in a single operative step. [source] Theoretical studies on the electronic and optical properties of two new alternating fluorene/carbazole copolymersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2005Li Yang Abstract Poly(fluorene)-type materials are widely used in polymer-based emitting devices. During operation there appears, however, an additional emission peak at around 2.3 eV, leading to both a color instability and reduced efficiency. The incorporation of the carbazole units has been proven to efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate two series of alternating fluorene/carbazole oligomers and copolymers poly[2,7-(N-(2-methyl)-carbazole)- co - alt -2,7-m(9,9-dimethylfluorene)], namely, PFmCz (m = 1,2) and gain a detailed understanding of the influence of carbazole units on the electronic and optical properties of fluorene derivatives. The electronic properties of the neutral molecules, HOMO-LUMO gaps (,H-L), in addition to the positive and negative ions, are studied using B3LYP functional. The lowest excitation energies (Egs) and the maximal absorption wavelength ,abs of PFmCz (m = 1,2) are studied, employing the time-dependent density functional theory (TD-DFT). The properties of the two copolymers, such as ,H-L, Eg, IPs, and EAs were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero (1/n = 0). The outcomes showed that the carbazole unit is a good electron-donating moiety for electronic materials, and the incorporation of carbazole into the polyfluorene (PF) backbone resulted in a broadened energy gap and a blue shift of both the absorption and photoluminescence emission peaks. Most importantly, the HOMO energies of PF1Cz and PF2Cz are both a higher average (0.4 eV) than polyfluorene (PF), which directly results in the decreasing of IPs of about 0.2 eV more than PF, indicating that the carbazole units have significantly improved the hole injection properties of the copolymers. In addition, the energy gap tends to broaden and the absorption and emission peaks are gradually blue-shifted to shorter wavelengths with an increase in the carbazole content in the copolymers. This is due to the interruption of the longer conjugation length of the backbone in the (F1Cz)n series. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 969,979, 2005 [source] | |||||||||||||