Generation of electron spin polarization in disordered organic semiconductors

TL;DR

This paper analyzes how electron spin polarization (ESP) arises in disordered organic semiconductors through quantum transitions during charge carrier recombination and quenching, considering different diffusion models and interactions.

Contribution

It introduces detailed models of ESP generation in disordered organic semiconductors, considering cage and free diffusion, and the effects of interactions, providing formulas for ESP estimation.

Findings

ESP can be significantly larger than thermal levels at room temperature.

Different diffusion models influence the magnitude of ESP.

Attractive interactions affect ESP generation mechanisms.

Abstract

The generation mechanisms of electron spin polarization (ESP) of charge carriers (electrons and holes, called "doublets") in doublet-doublet recombination and triplet-doublet quenching in disordered organic semiconductors are analyzed in detail. The ESP is assumed to result from quantum transitions between the states of the spin Hamiltonian of the pair of interacting particles. The value of the ESP is essentially determined by the mechanism of relative motion of particles. In our work we have considered the cage and free diffusion models. The effect of possible attractive spin-independent interactions between particles is also analyzed. Estimation with obtained formulas shows that the proposed mechanisms can lead to a fairly strong ESP much larger than the thermal one (at room temperatures)