Theoretical investigation on thermal effect in organic semiconductors

Abstract

Thermal effect on a neutral and a doped polymer chain is studied in the frame work of Su–Schrieffer–Heeger tight-binding model considering electronic Fermi–Dirac distribution as well as atomic square-random distribution. It is found that in a neutral polymer chain, the band gap is decreasing as the temperature increases. For a doped polymer chain, extra electrons will occupy high energy levels. The localization and stability of the electronic self-trapped state will decrease with temperature. We also show that at temperature high enough (⩾340K in present parameters), a hot electron will get rid of the trap of the lattice and become extended over the whole polymer molecule. In addition, the effects of the quantity of charge carriers and the electron–phonon coupling at room temperature are also investigated.