Recombination of polaron and exciton in conjugated polymers.

Both polarons and excitons, which are composite particles with internal lattice structure, play an important role in the transport and light-emitting properties of conjugated polymers for the use in, e.g., polymer based light-emitting diodes (LEDs). The scattering and recombination processes between a triplet exciton and a polaron are investigated using a nonadiabatic evolution method based on an extended Su-Schrieffer-Heeger model including interchain interactions. The results show that an excited polaron state can be formed, besides a triplet exciton is converted into a singlet exciton by the polaron. Moreover, the yields of both the singlet exciton and the excited polaron states increase with increasing interchain coupling strength. The excited polaron is luminescent due to radiative decay as is the singlet exciton. Therefore, our results indicate that the quantum efficiency of polymer LEDs could be enhanced by polaron-exciton recombination.

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

[2]  D. Moses,et al.  Pressure dependence of the photoabsorption of polyacetylene , 1982 .

[3]  Franco Cacialli,et al.  Molecular-scale interface engineering for polymer light-emitting diodes , 2000, Nature.

[4]  S. Horng,et al.  Triplet exciton formation and decay in polyfluorene light emitting diode , 2005 .

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

[6]  Shuai,et al.  Singlet and triplet exciton formation rates in conjugated polymer light-emitting diodes , 2000, Physical review letters.

[7]  S. Ramasesha,et al.  Electron correlation effects in electron-hole recombination in organic light-emitting diodes , 2003 .

[8]  S. Ramasesha,et al.  Formation cross-sections of singlet and triplet excitons in π-conjugated polymers , 2001, Nature.

[9]  C. Q. Wu,et al.  Dynamics of photogenerated polarons in conjugated polymers. , 2004, Physical review letters.

[10]  David Beljonne,et al.  Triplet formation and decay in conjugated polymer devices , 2002 .

[11]  Campbell,et al.  First-principles calculations of the three-dimensional structure and intrinsic defects in trans-polyacetylene. , 1990, Physical review. B, Condensed matter.

[12]  A. S. Dhoot,et al.  Spin-dependent exciton formation in π-conjugated compounds , 2001, Nature.

[13]  S. Stafström,et al.  Polaron dynamics in a system of coupled conjugated polymer chains , 2001 .

[14]  M. P. Lima,et al.  Dynamical evolution of polaron to bipolaron in conjugated polymers , 2006 .

[15]  Yong Cao,et al.  Improved quantum efficiency for electroluminescence in semiconducting polymers , 1999, Nature.

[16]  M. Gibbs,et al.  Magnetoresistance and efficiency measurements of Alq 3 -based OLEDs , 2007 .

[17]  E. Conwell,et al.  Nonlinear dynamics of an added carrier in trans-polyacetylene in the presence of an electric field , 2000 .

[18]  W. Barford.  Theory of singlet exciton yield in light-emitting polymers , 2004, physics/0410252.

[19]  Donal D. C. Bradley,et al.  Conjugated polymer electroluminescence , 1993 .

[20]  Alan J. Heeger,et al.  Soliton excitations in polyacetylene , 1980 .

[21]  H. Streitwolf.  DYNAMICS OF A BOND-DISORDERED PEIERLS CHAIN AND MIXED GAP STATES , 1998 .

[22]  C. Q. Wu,et al.  Interchain coupling effects on dynamics of photoexcitations in conjugated polymers. , 2008, The Journal of chemical physics.

[23]  C. Q. Wu,et al.  Dynamical study on polaron formation in a metal/polymer/metal structure , 2003 .

[24]  J. Hubbard.  Electron correlations in narrow energy bands , 1963, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[25]  K. Nasu,et al.  Photoinduced polarization inversion in a polymeric molecule , 2000, Physical review letters.

[26]  D. Hertel,et al.  Triplet-polaron quenching in conjugated polymers. , 2007, The journal of physical chemistry. B.

[27]  S. Block,et al.  Nucleation of optically excited solitons and breathers in trans-polyacetylene , 1996 .

[28]  J. Brédas,et al.  Chain‐Length Dependence of Singlet and Triplet Exciton Formation Rates in Organic Light‐Emitting Diodes , 2004 .

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

[30]  Ruth Shinar,et al.  Organic light-emitting devices (OLEDs) and OLED-based chemical and biological sensors: an overview , 2008 .