Image-enhanced bipolaron formation at organic semiconductor/electrode interfaces

Jonathon R. Schrecengost, Sukrit Mukhopadhyay, and Noel C. Giebink
Phys. Rev. B 102, 165311 – Published 21 October 2020

Abstract

We explore the image charge interaction for organic semiconductor bipolarons near a conducting interface and find that the cross term between one of the constituent charges and the image of its neighbor stabilizes the bipolaron by up to ∼0.3 eV, dramatically increasing the concentration of this species near the interface. Using density functional theory calculations for the common hole transport molecule N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine, we validate a simple point charge description of this effect and incorporate it within an interface energy level alignment model to predict the density of polarons and bipolarons near the interface. We find that the image effect greatly enhances bipolaron formation in the first few monolayers, leading to the expectation that bipolarons account for more than 1% of the total interface charge in many cases of practical interest. This result reinforces the notion that bipolarons are robust near the contacts of many organic semiconductor devices and thus helps to rationalize their involvement in the phenomenon of unipolar organic magnetoresistance.

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  • Received 8 July 2020
  • Revised 21 September 2020
  • Accepted 6 October 2020

DOI:https://doi.org/10.1103/PhysRevB.102.165311

©2020 American Physical Society

Physics Subject Headings (PhySH)

Polymers & Soft Matter

Authors & Affiliations

Jonathon R. Schrecengost1, Sukrit Mukhopadhyay2, and Noel C. Giebink3,*

  • 1Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
  • 2The Dow Chemical Company, 1776 Building, Midland, Michigan 48674, USA
  • 3Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA

  • *ncg2@psu.edu

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Issue

Vol. 102, Iss. 16 — 15 October 2020

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