Spontaneous Polarization Induced by Side Chains in Ordered Poly(3-hexylthiophene)

Abstract

We have found that ordered poly­(3-hexylthiophene) (P3HT) exhibits spontaneous polarization along the backbone direction. This effect is caused by the lack of inversion symmetry due to head-to-tail side-chain arrangement. We have also shown that spontaneous polarization in ordered P3HT keeps significant values even at room temperature when the effects of thermal disorder are important. Consequently, it has a strong effect on electronic properties of the material. For example, at the interface between the crystalline and amorphous domain in P3HT, the electric field caused by spontaneous polarization confines the delocalized HOMO state to one side of the crystalline domain.

Sign flipping of spontaneous polarization in vapour-deposited films of small polar organic molecules

“…This counter-intuitive phenomenon was reported 50 years ago, 1 but has not been studied extensively either at cryogenic temperatures or near room temperature; [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] the small number of research groups involved in such studies tended to concentrate on very few compounds, when a lot of information is lacking. What is known about this effect is limited to four facts: (i) condensing molecules need to have a dipole moment; (ii) voltages observed are proportional to the thickness of the condensate films, i.e., this is a bulk rather than a surface effect; (iii) the nature of the substrate is immaterial; (iv) the films thus created exist in a metastable state and the voltage is eliminated when the films are heated and not recovered upon re-cooling.…”

Multiscale in modelling and validation for solar photovoltaics

“…Subsequently, effective hopping rates, carrier lifetimes and mobilities can be extracted from KMC simulations and inserted into a macroscopic driftdiffusion-Poisson solver, thus linking from mesoscopic to macroscopic scales [76]. The electronic structure and polarization at organic interfaces can also be studied on ab initio level using the charge patching method within DFT [77] or DFT-based tight-binding [78], and exciton formation as well as ultra-fast separation of photogenerated charge carriers at such interfaces have been assessed based on a density matrix formalism [79,80].…”