Using Dopants as Agents to Probe Key Electronic Properties of Organic Semiconductors

TL;DR

This paper presents a novel approach using dopants as probes to measure fundamental electronic properties like ionization potential, electron affinity, and Coulomb interaction energy in organic semiconductors, enhancing understanding of material behavior.

Contribution

It introduces a method that leverages doping processes and combined experimental and simulation data to directly estimate key electronic parameters of organic materials.

Findings

Estimation of mean ionization potential and electron affinity from doping data

Determination of Coulomb interaction energy in charge-transfer complexes

Enhanced understanding of dopant effects on organic electronic properties

Abstract

In organic electronics, conductivity doping is used primarily to eliminate charge injection barriers in organic light-emitting diodes, organic photovoltaics and other electronic devices. Therefore, research on conductivity doping is primarily focused on understanding and enhancing the properties of these doped layers. In contrast, this work shifts the focus from optimizing doped layers to leveraging the doping process as a tool for investigating fundamental material properties. Specifically, the dopant is used as an "agent" to enable the measurement of three critical parameters: ionization potential (IP), electron affinity (EA), and Coulomb interaction energy (VC) - that govern dopant ionization and play central roles in organic electronic devices in general. While these parameters can be measured experimentally, conventional approaches often involve intricate or indirect methods, such as spectral deconvolution, which may introduce ambiguities or fail to represent bulk properties. Here it is shown how consolidating the experimental data and simulations on the dopant ionization fraction and doped-induced conductivity can be used to estimate the mean IP or EA of the embedded organic molecule, and VC of the embedded charge-transfer complex. These results illustrate how measuring and simulating doped materials can provide access to the fundamental design parameters of organic electronic devices