Magnetic field effects on electron-hole recombination in disordered organic semiconductors

TL;DR

This paper analyzes how magnetic fields influence electron-hole recombination in disordered organic semiconductors using a stochastic Liouville equation approach, deriving formulas for different models and mechanisms.

Contribution

It introduces a general method and explicit formulas to analyze magnetic field effects on recombination, considering various spin relaxation mechanisms and motion models.

Findings

Different magnetic field dependences of recombination yield and rate are identified.

Formulas derived are useful for interpreting experimental data.

The approach accounts for hyperfine, Zeeman, and Δg mechanisms.

Abstract

Characteristic properties of magnetic field effects on spin selective geminate and bulk electron-hole polaron pair (PP) recombination are analyzed in detail within the approach based on the stochastic Liouville equation. Simple expressions for the magnetic field (B) dependence of recombination yield and rate are derived within two models of relative PP motion: free diffusion and diffusion in the presence of well (cage). The spin evolution of PPs is described taking in account the relaxation induced by hyperfine interaction, anisotropic part of the Zeeman interaction induced, as well as $\Delta g$-mechanism. A large variety of the $B$-dependences of the recombination yield $Y(B)$ and rate $K(B)$ is obtained depending on the relative weights of above-mentioned mechanisms. The proposed general method and derived particular formulas are shown to be quite useful for the analysis of recent experimental results.