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Electroluminescence from PVK-based polymer blends with metal complex dyes
Keith C. Gordon,Penny J. Walsh,Elise M. McGale 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
Organic light-emitting diodes may be fabricated using transition metal complexes as the emitting molecules. These have some advantages because of their photo-robustness and because they may be engineered to be very eective charge-carriers thus readily being excited by EL excitation.
Reish, Matthew E.,Huff, Gregory S.,Lee, Wonho,Uddin, Mohammad Afsar,Barker, Alex J.,Gallaher, Joseph K.,Hodgkiss, Justin M.,Woo, Han Young,Gordon, Keith C. American Chemical Society 2015 Chemistry of materials Vol.27 No.8
<P>The electronic properties of the donor–acceptor (DA) polymer poly{5,6-bis(octyloxy)-4-(thiophen-2-yl)benzo[<I>c</I>]-1,2,5-thiadiazole} (PTBT) have been investigated using spectroscopic and computational techniques. Electronic absorption and emission spectra reveal the presence of an ordered and a disordered phase in solution. Franck–Condon modeling of the ordered phase yields Huang–Rhys factors of 0.55 (20 °C) and 0.51 (−180 °C), indicating little structural distortion between ground and excited state. DFT calculations with resonance Raman spectroscopy are consistent with a lowest energy excited state that is electronically delocalized and has little charge-transfer character, unexpected for a copolymer with a low bandgap (∼1.8 eV). Transient absorption spectroscopy of PTBT:fullerene blends reveals near-unity internal charge-transfer yields in both ordered and disordered film morphologies. In the disordered blend, charge transfer is complete within the laser pulse (100 fs), whereas the ordered blend also features a slower phase due to exciton diffusion in the phase separated morphology. In the ordered blend, the spectra and dynamics of charge transfer reveal that excitons and charges promptly occupy delocalized states on extended polymer chains. The pervasive use of donor–acceptor structures in polymer devices makes understanding the interplay of morphology and electronic structure of these polymers essential and here a spectroscopic and computational investigation gives an extensive picture of the electronic properties and their effect on charge dynamics in a DA polymer.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-8/cm504655f/production/images/medium/cm-2014-04655f_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm504655f'>ACS Electronic Supporting Info</A></P>
Resonance Raman intensity analysis of an intramolecular charge-transfer process
Sarah L. Howell,Keith C. Gordon,Mark R. Waterland 한국물리학회 2006 Current Applied Physics Vol.6 No.3
We present an analysis of the resonance Raman intensities of an intramolecular charge-transfer transition using a time-domain for-mulation of the Raman scattering process. This analysis provides mode-specic reorganization energies for the vibrational modes thatcouple to the photoinduced charge-transfer event. In addition, the absolute magnitude of the resonance Raman intensities allows thesurrounding solvent contribution to the reorganization energy to also be determined. The analysis demonstrates that for the intramo-tion energies.
A Spectroscopic and DFT Study of the Electronic Properties of Carbazole-Based D–A Type Copolymers
Reish, Matthew E.,Nam, Sanghun,Lee, Wonho,Woo, Han Young,Gordon, Keith C. American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.40
<P>The structural and electronic properties of three carbazole containing copolymers used in organic photovoltaic applications, poly[<I>N</I>-1-octylnonyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT), poly[<I>N</I>-1-octylnonyl-2,7-carbazole-alt-4,7-(2′,1′,3′-benzothiadiazole)] (PCBT), and poly[<I>N</I>-1-octylnonyl-2,7-carbazole-alt-4,7-(2′,1′,3′-benzoselenadiazole)] (PCBSe) have been studied using resonance Raman (RR) and transient absorption (TA) spectroscopies and density functional theory (DFT) calculations. Enhancement of Raman modes centered on the acceptor unit when a Raman excitation wavelength is coincident with lowest energy electronic excitation suggests that the excitation involves charge transfer from the carbazole donor to the varying benzodiazole acceptors. The pattern of the enhancement when the excitation wavelength is coincident with the higher energy transition indicates that this transition is π to π* in nature; this is consistent with TD-DFT calculations. Nanosecond transient absorption studies show long-lived excited state signals for PCDTBT (126 ± 4 ns and 1.56 ± 0.1 μs) and PCBSe (1.82 ± 0.1 μs), suggesting that population of the triplet state is appreciable. No transient signal could be detected in PCBT. B3LYP TD-DFT calculations of the monomer through to the hexamer indicate a broadly delocalized excited state orbital for PCDTBT as indicated by the linear decrease in excitation energy with an increased number of repeat units, while for PCBSe and PCBT, the reduction in excitation is sublinear. The highest occupied (HOMO) and lowest unoccupied molecular orbitals (LUMO) of PCBSe and PCBT polymers compared to PCDTBT are similarly diffuse, but the population of higher order orbitals is decreased when compared with PCDTBT. CAM-B3LYP calculations reduce the delocalization of the frontier orbitals and show less reduction in excitation energy with additional repeat units for each polymer.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-40/jp307552z/production/images/medium/jp-2012-07552z_0012.gif'></P>
Salicylic Acid-Based Organic Dyes Acting as the Photosensitizer for Solar Cells
Hong, Sungjun,Park, Jae-Hyeong,Han, Ah-Reum,Ko, Kwan-Woo,Eom, Jin Hee,Namgoong, Sung Keon,Lo, Alvie S. V.,Gordon, Keith C.,Yoon, Sungho,Han, Chi-Hwan American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.5
<P>A D-pi-A metal-free organic dye, featuring salicylic acid as a novel acceptor/anchoring unit, has been designed, synthesized and applied to dye-sensitized solar cell. The detailed photophysical, electrochemical, photovoltaic and sensitizing properties of the organic dye were investigated, in addition to the computational studies of the dye and dye-(TiO2)(6) system. A solar cell device using this new organic dye as a sensitizer produced a solar to electric power conversion efficiency (PCE) of 3.49% (J(SC) = 6.69 mAcm(-2), V-OC 0.74 V and ff = 0.70) under 100 mWcm(-2) simulated AM 1.5 G solar irradiation, demonstrating that the salicylic acid-based organic dye is a suitable alternative to currently used organometallic dyes.</P>