Absorption and emission in pinwheel aggregates of oligo-phenylene vinylene molecules

被引:53
作者
Spano, FC [1 ]
机构
[1] Temple Univ, Dept Chem, Philadelphia, PA 19122 USA
关键词
D O I
10.1063/1.1349056
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The effects of exciton-vibrational coupling and point defects on the absorption and emission of distyrylbenzene nanoaggregates are treated theoretically. Two aggregate types based on a two-dimensional array of cyclic tetramers (pinwheels) are considered: type A aggregates, composed of chiral pinwheels, and type B aggregates, composed of achiral pinwheels. The low-energy vibronic features in the experimental excitation spectrum arise from vibrationally dressed K = (0,0) excitons, while the more intense blue shifted H-band is due to nearly free K = (0,0) excitons. The K = (0,0) features are polarized primarily along the herringbone plane normal. The lowest Davydov component is polarized in the herringbone plane and is due to the lowest energy K = (pi,pi) exciton. This state is also responsible for the aggregate emission. The 0-upsilon peaks for v >0 are mainly due to indirect transitions to the ground electronic state containing v phonons, with wave vector sum equal to (pi,pi). These peaks are largely independent of defect fraction and are polarized primarily along the herringbone plane normal. In stark contrast, the 0-0 emission critically depends on the concentration of point defects and is polarized entirely in the herringbone plane. This wavelength dependent emission polarization is in full agreement with experimental observations. Type A aggregates are weakly emissive, with the 0-0 emission peak vanishing in defect-free aggregates and increasing with defect concentration. The reverse holds for type B aggregates: the 0-0 intensity scales with the number of molecules in the aggregate and decreases with defect concentration. Sufficiently large type B aggregates are superradiant, and may be used to enhance the quantum yield in optical devices such as light-emitting diodes. (C) 2001 American Institute of Physics.
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页码:5376 / 5390
页数:15
相关论文
共 37 条
[1]   Synthesis and optical properties of oligo- and poly(2,5-dialkoxy-1,4-para-phenylenevinylene)s [J].
Barashkov, NN ;
Guerrero, DJ ;
Olivos, HJ ;
Ferraris, JP .
SYNTHETIC METALS, 1995, 75 (02) :153-160
[2]   Interchain interactions in conjugated materials:: The exciton model versus the supermolecular approach [J].
Beljonne, D ;
Cornil, J ;
Silbey, R ;
Millié, P ;
Brédas, JL .
JOURNAL OF CHEMICAL PHYSICS, 2000, 112 (10) :4749-4758
[3]   Exciton dynamics in poly(p-pyridyl vinylene) [J].
Blatchford, JW ;
Jessen, SW ;
Lin, LB ;
Lih, JJ ;
Gustafson, TL ;
Epstein, AJ ;
Fu, DK ;
Marsella, MJ ;
Swager, TM ;
MacDiarmid, AG ;
Yamaguchi, S ;
Hamaguchi, H .
PHYSICAL REVIEW LETTERS, 1996, 76 (09) :1513-1516
[4]   LIGHT-EMITTING-DIODES BASED ON CONJUGATED POLYMERS [J].
BURROUGHES, JH ;
BRADLEY, DDC ;
BROWN, AR ;
MARKS, RN ;
MACKAY, K ;
FRIEND, RH ;
BURN, PL ;
HOLMES, AB .
NATURE, 1990, 347 (6293) :539-541
[5]   Interchain photoluminescence in poly(phenylene vinylene) derivatives [J].
Conwell, EM ;
Perlstein, J ;
Shaik, S .
PHYSICAL REVIEW B, 1996, 54 (04) :R2308-R2310
[6]   Photoluminescence spectra of oligo-paraphenylenevinylenes: a joint theoretical and experimental characterization [J].
Cornil, J ;
Beljonne, D ;
Heller, CM ;
Campbell, IH ;
Laurich, BK ;
Smith, DL ;
Bradley, DDC ;
Mullen, K ;
Bredas, JL .
CHEMICAL PHYSICS LETTERS, 1997, 278 (1-3) :139-145
[7]   Influence of interchain interactions on the absorption and luminescence of conjugated oligomers and polymers:: A quantum-chemical characterization [J].
Cornil, J ;
dos Santos, DA ;
Crispin, X ;
Silbey, R ;
Brédas, JL .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1998, 120 (06) :1289-1299
[8]   LOCAL ENERGETIC DISORDER IN MOLECULAR AGGREGATES PROBED BY THE ONE-EXCITON TO 2-EXCITON TRANSITION [J].
DURRANT, JR ;
KNOESTER, J ;
WIERSMA, DA .
CHEMICAL PHYSICS LETTERS, 1994, 222 (05) :450-456
[9]   Characterization of oriented oligo(phenylenevinylene) films and nano-aggregates by UV/Vis-absorption and fluorescence spectroscopy [J].
Egelhaaf, HJ ;
Gierschner, J ;
Oelkrug, D .
SYNTHETIC METALS, 1996, 83 (03) :221-226
[10]   Cylindrical microlasers and light emitting devices from conducting polymers [J].
Frolov, SV ;
Fujii, A ;
Chinn, D ;
Vardeny, ZV ;
Yoshino, K ;
Gregory, RV .
APPLIED PHYSICS LETTERS, 1998, 72 (22) :2811-2813