Critical temperature and products of intrachain polaron recombination in conjugated polymers

Abstract

The intrachain recombination dynamics between oppositely charged polarons is theoretically investigated through the use of a version of the Su-Schrieffer-Heeger (SSH) model modified to include an external electric field, an extended Hubbard model, Coulomb interactions, and temperature effects in the framework of a nonadiabatic evolution method. Our results indicate notable characteristics concerning the polaron recombination: (1) it is found that there exists a critical temperature regime, below which an exciton is formed directly and (2) a pristine lattice is the resulting product of the recombination process, if the temperature is higher than the critical value. Additionally, it is found that the critical electric field regime plays the role of drastically modifying the system dynamics. These facts suggest that thermal effects in the intrachain recombination of polarons are crucial for the understanding of electroluminescence in optoelectronic devices, such as Polymer Light Emitting Diodes.

Same polarity polaron and bipolaron scattering on conducting polymers

“…Several studies has been carried out on the dynamics of scattering involving opposite charged quasi-particles [7][8][9][10][11], but we could not find any on quasi-particles with same sign charges. The present work addresses such situations in pristine chains of cispolyacetilene and polyparaphenylene, both simple and prototypical polymers whose analysis is relatively easy and can shed light on more complex systems.…”

Charge Carrier Scattering in Polymers: A New Neutral Coupled Soliton Channel

“…The occupation number is derived according to ref. 25 . The combined analysis of these two measurements has proven to be an interesting manner to drawn general conclusions concerning the nature of the states yielded after the collisional processes, particularly when it comes to that of oppositely charged species 40–44 .…”

“…We summarize our results with an analysis of two phase diagrams relating the yield of formation of the soliton–antisoliton pair (percentuals in the the color scale) to the electric field, and the Hubbard parameters U and V. Such property is a measure of how efficient is the formation of the structure and its definition is given in the literature 25 . Figure 4(a) presents the yield of formation of the soliton–antisoliton pair as a function of the electric field and U.…”

“…Such physical picture is achieved by employing the self-consistent procedure described in a previous work 25 . In the formation processes of these charge carriers, two electrons are added (electron-bipolaron) or removed (hole-bipolaron) from the polymer lattice generating distortions in its conformation and displacement of energy levels inside the band gap.…”

“…Once obtained the initial arrangement for the lattice, the system is evolved in time by using Coupled Dynamics, as established in ref. 25 . The set of parameters employed in the model Hamiltonian used here is: t 0  = 2.5 eV, M  = 1349.14 eV × fs 2 /Å 2 , K  = 21 eV/Å 2 , V  =  U /3, δ 0  = 0.005 eV, and a  = 1.22 Å.…”