Theoretical investigation of the lowest singlet and triplet states in poly(paraphenylene vinylene)oligomers

Using the semiempirical intermediate neglect of differential overlap (INDO) Hamiltonian in combination with configuration interaction techniques, we calculate the optical and photoinduced absorption spectra of poly(paraphenylene vinylene) oligomers containing from two to five phenyl rings; the evolutions with chain length of the singlet–singlet and triplet–triplet excitation energies as well as the values extrapolated for the polymer are in good agreement with experiment. The geometry relaxation phenomena in the first one‐photon allowed singlet excited state and in the lowest triplet state are modeled on the basis of either bond‐order/bond‐length relationships or the formation of (bi)polaron‐type defects; the results are compared to those of direct geometry optimizations in the excited state. The different methods consistently lead to more pronounced bond‐length modifications in the triplet state than in the singlet state.

[1]  Wong,et al.  Nonlinear optical properties of linear chains and electron-correlation effects. , 1988, Physical review. B, Condensed matter.

[2]  Bradley,et al.  Electroluminescence-detected magnetic-resonance study of polyparaphenylenevinylene (PPV)-based light-emitting diodes. , 1992, Physical review. B, Condensed matter.

[3]  J. Brédas,et al.  Nature of photoexcitations in poly (paraphenylene vinylene) and its oligomers , 1994 .

[4]  Yoshino,et al.  Optically detected magnetic resonance study of polaron and triplet-exciton dynamics in poly(3-hexylthiophene) and poly(3-dodecylthiophene) films and solutions. , 1990, Physical review letters.

[5]  A. Heeger,et al.  Nature of the primary photoexcitations in poly(arylene-vinylenes) , 1994 .

[6]  Michael Mehring,et al.  Electronic Properties of Conjugated Polymers III , 1987 .

[7]  D. McClure,et al.  Ultraviolet Spectra of Stilbene, p‐Monohalogen Stilbenes, and Azobenzene and the trans to cis Photoisomerization Process , 1962 .

[8]  R. Friend,et al.  Optical spectroscopy of highly ordered poly(p-phenylene vinylene) , 1993 .

[9]  J. Brédas,et al.  Theoretical study of thiophene oligomers: Electronic excitations, relaxation energies, and nonlinear optical properties , 1993 .

[10]  Dixit,et al.  Essential-states mechanism of optical nonlinearity in pi -conjugated polymers. , 1991, Physical review. B, Condensed matter.

[11]  R. L. Elsenbaumer,et al.  Handbook of conducting polymers , 1986 .

[12]  D. Campbell,et al.  Optical absorption from polarons in a model of polyacetylene , 1983 .

[13]  Lane,et al.  Polarons and triplet polaronic excitons in poly(paraphenylenevinylene) (PPV) and substituted PPV: An optically detected magnetic resonance study. , 1991, Physical review. B, Condensed matter.

[14]  Choi,et al.  Excited polarons in poly(phenylene vinylene) and poly(diacetylene). , 1991, Physical review. B, Condensed matter.

[15]  Robert J. Buenker,et al.  Individualized configuration selection in CI calculations with subsequent energy extrapolation , 1974 .

[16]  H. Bässler,et al.  Absorption spectra of the anions of phenylenevinylene oligomers and polymer , 1991 .

[17]  Dixit,et al.  Role of the conduction band in electroabsorption, two-photon absorption, and third-harmonic generation in polydiacetylenes. , 1993, Physical review. B, Condensed matter.

[18]  Klaus Schulten,et al.  The low‐lying electronic excitations in long polyenes: A PPP‐MRD‐CI study , 1986 .

[19]  B. Pierce.  A theoretical analysis of third‐order nonlinear optical properties of linear polyenes and benzene , 1989 .

[20]  Paul D. Townsend,et al.  Photo-excitation in conjugated polymers , 1987 .

[21]  J. Kagan,et al.  EXCITED STATE PROPERTIES OF ∝aL‐TERTHIENYL and RELATED MOLECULES , 1985, Photochemistry and photobiology.

[22]  Jean-Luc Brédas,et al.  Conjugated polymers : the novel science and technology of highly conducting and nonlinear optically active materials , 1991 .

[23]  Bradley,et al.  Photoexcited states in poly(p-phenylene vinylene): Comparison with trans,trans-distyrylbenzene, a model oligomer. , 1990, Physical review. B, Condensed matter.

[24]  A. Heeger,et al.  Visible light emission from semiconducting polymer diodes , 1991 .

[25]  J. Brédas,et al.  Nonlinear optical processes in short polyenes: Configuration interaction description of two-photon absorption and third-harmonic generation , 1992 .

[26]  J. Michl,et al.  Polysilane high polymers , 1989 .

[27]  G. Weiser,et al.  One-Dimensional Wide Energy Bands in a Polydiacetylene Revealed by Electroreflectance , 1981 .

[28]  N. S. Sariciftci,et al.  TRIPLET-STATE PHOTOEXCITATIONS OF OLIGOTHIOPHENE FILMS AND SOLUTIONS , 1994 .

[29]  Conwell,et al.  Excitons and the band gap in poly(phenylene vinylene). , 1993, Physical review. B, Condensed matter.

[30]  R. Silbey,et al.  Comparative theoretical study of the doping of conjugated polymers: Polarons in polyacetylene and polyparaphenylene , 1982 .

[31]  Donal D. C. Bradley,et al.  The photovoltaic response in poly(p-phenylene vinylene) thin-film devices , 1994 .

[32]  J. Brédas,et al.  Polarons, bipolarons, and solitons in conducting polymers , 1985 .

[33]  S. Holdcroft,et al.  First observation of phosphorescence from .pi.-conjugated polymers , 1993 .

[34]  T. Azumi,et al.  Phosphorescence of the trans-stilbene single crystal , 1985 .

[35]  D. McClure,et al.  The lowest triplet state of stilbene. , 1968, Journal of the American Chemical Society.

[36]  Alan J. Heeger,et al.  Solitons in polyacetylene , 1979 .

[37]  F. E. Karasz,et al.  Ultraviolet and visible spectroscopy of poly(paraphenylene vinylene) , 1987 .

[38]  R. N. Marks,et al.  Light-emitting diodes based on conjugated polymers , 1990, Nature.

[39]  Alan J. Heeger,et al.  Solitons in conducting polymers , 1988 .

[40]  Wei,et al.  Optical probes of excited states in poly(p-phenylenevinylene). , 1994, Physical review letters.

[41]  R. Friend,et al.  Photoexcitation in poly(p-phenylene vinylene) , 1989 .

[42]  Etemad,et al.  Excitation and relaxation energies of trans-stilbene: Confined singlet, triplet, and charged bipolarons. , 1993, Physical review. B, Condensed matter.

[43]  F. E. Karasz,et al.  Nonplanarity and ring torsion in poly(p‐phenylene vinylene). A neutron‐diffraction study , 1993 .

[44]  Eamonn F. Healy,et al.  Development and use of quantum mechanical molecular models. 76. AM1: a new general purpose quantum mechanical molecular model , 1985 .

[45]  Z. Soos,et al.  Valence bond approach to exact nonlinear optical properties of conjugated systems , 1989 .

[46]  R. Friend,et al.  Optical spectra and excitations in phenylene vinylene oligomers , 1993 .

[47]  Michael C. Zerner,et al.  An intermediate neglect of differential overlap technique for spectroscopy: Pyrrole and the azines , 1973 .