Relaxation energies and excited state structures of poly(para-phenylene)

Abstract

We investigate the relaxation energies and excited state geometries of the light emitting polymer, poly(para-phenylene). We solve the Pariser-Parr-Pople-Peierls model using the density matrix renormalization group method. We find that the lattice relaxation of the dipole-active $1^1{B}_{1u}^{-}$ state is quite different from that of the $1^3{B}_{1u}^{+}$ state and the dipole-inactive $2^1{A}_g^{+}$ state. In particular, the $1^1{B}_{1u}^{-}$ state is rather weakly coupled to the lattice and has a rather small relaxation energy ca. 0.1 eV. In contrast, the $1^3{B}_{1u}^{+}$ and $2^1{A}_g^{+}$ states are strongly coupled with relaxation energies of ca. 0.5 and ca. 1.0 eV, respectively. By analogy to linear polyenes, we argue that this difference can be understood by the different kind of solitons present in the $1^1{B}_{1u}^{-}$, $1^3{B}_{1u}^{+}$ and $2^1{A}_g^{+}$ states. The difference in relaxation energies of the $1^1{B}_{1u}^{-}$ and $1^3{B}_{1u}^{+}$ states accounts for approximately one-third of the exchange gap in light-emitting polymers.

arXiv commentSubmitted to Physical Review B

References in corpus (6)

• Electron correlation effects in electron-hole recombination in organic light-emitting diodes
• Theory of the singlet exciton yield in light-emitting polymers
• Structural relaxations in electronically excited poly(para-phenylene)
• Excited states of linear polyenes
• Electron-lattice relaxation, and soliton structures and their interactions in polyenes
• Large scale numerical investigation of excited states in poly(phenylene)

Cited by in corpus (2)

• New Trends in Density Matrix Renormalization
• Dynamical simulations of charged soliton transport in conjugated polymers with the inclusion of electron-electron interactions