Ground and excited state nonlinear optical properties of poly(-para phenylene vinylene)

Abstract

We investigate theoretically the nature of higher energy excited even as well as odd parity states, for various sizes of oligomers of PPV. We study in detail various nonlinear optical properties, like third harmonic generation (THG), two photon absorption (TPA), electro absorption (EA) of oligomers of PPV within a rigid band correlated Pariser-Parr-Pople (PPP) model Hamiltonian, using the π-electron basis and the powerful multireference single and double configuration interaction (MRSDCI) method. We also use single-double-triple-quadruple configuration interaction (SDTQCI) in limited cases. We show that in THG three kinds of one photon states 1Bu, jBu and nBu (where j < n) whereas three kinds of even parity states 2Ag, mAg and kAg appear. The even parity states 2Ag, mAg and kAg also appear in TPA. While mAg absorptions appear just after the nBu, the 2Ag appears immediately after the jBu absorptions. A detailed analysis of the wavefunctions of higher energy excited states with conjugation length are presented. We show that beyond certain conjugation length that both mAg and kAg states mainly involve excitations between the lowest delocalized valance and conductance bands. Our study indicate middle order exciton binding energy. Finally, we theoretically predict that by optically exciting PPV at one wavelength equivalent to the optical gap for a sufficiently long time to perform nonlinear optical measurement, the values of χ can be enhanced by three orders-of-magnitude.

Role of Geometric Distortion and Polarization in Localizing Electronic Excitations in Conjugated Polymers

“…Several experimental − and theoretical studies − performed earlier have highlighted the diffusion and mobility properties for excitons and polarons in substituted PPVs. Calculations have predicted the self-trapping of the electronic excitations due to vibrational relaxation. − Also, neutral and charged excitation processes have been studied using time-dependent density functional theory (TD-DFT) for determining the electro-optical properties of PPV light emitting diodes .…”

DFT modeling of conjugated copolymers photophysical properties: Towards organic solar cell application

“…In order to improve their performance, a new category of polymers, with donor-acceptor (D-A) architectures [5], including alternating copolymers, blended and/or multilayers have been investigated [6]. Indeed, different polymers or oligomers have been widely investigated as an electron donor such as poly(p-phenylene vinylene) (PPV), polyfluorene (PF) derivatives [7][8][9][10] and poly (3-hexylthiophene) (P3HT) [11][12][13].…”

Estudo atomístico da desordem eletrônica em filmes amorfos de polímeros conjugados

“…Esse polímero, bem como seu derivado MEH-PPV (metil-etil-hexiloxi-PPV), reunem facilidade de síntese e processamento, e característicasóticas e eletrônicas atraentes, que justificam o seu emprego intenso nos estudos de ciência básica em busca da compreensão dos processos e mecanismos fundamentais envolvidos na geração e migração de carga em filmes [14].…”