Electrically Detected Magnetic Resonance Modeling and Fitting: An Equivalent Circuit Approach

TL;DR

This paper introduces an equivalent circuit model for cw-EDMR that accounts for the entire measurement circuit, improving understanding and fitting of EDMR spectra for materials like OLEDs and a-Si:H.

Contribution

The paper presents a novel circuit-based model for EDMR signals, including the measurement setup, enabling more accurate spectral analysis and parameter extraction.

Findings

Successfully modeled EDMR spectra from OLEDs and a-Si:H.

Enabled precise determination of g-factor and linewidth.

Improved understanding of circuit influences on EDMR signals.

Abstract

Continuous-wave electrically detected magnetic resonance (cw-EDMR or just EDMR) and its variants are powerful tools to investigate spin-dependent processes in materials and devices. The use of quadrature detection improves the quality and selectivity of EDMR analysis by allowing, for example, the separation of individual resonant spin lines. Here we propose an equivalent circuit model in order to better understand the EDMR quadrature signal in a variety of different situations. The model considers not just the electrical response of the sample but of cables and measuring circuit and its influence on the resulting spectral lines. Recent EDMR spectra from Alq3 based OLEDs, as well as from a-Si:H reported in the literature, were successfully described by the model. Moreover, the model allows the implementation of a fitting routine that can be easily used to determine accurate values of crucial parameters such as g-factor and linewidth of the resonant lines.