A generalized Stark effect electromodulation model for extracting excitonic properties in organic semiconductors

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Detail(s)

Original languageEnglish
Article number5089
Journal / PublicationNature Communications
Volume10
Online published8 Nov 2019
Publication statusPublished - 2019

Link(s)

Abstract

Electromodulation (EM) spectroscopy, a powerful technique to monitor the changes in polarizability p and dipole moment u of materials upon photo-excitation, can bring direct insight into the excitonic properties of materials. However, extracting Δp and Δu from the electromodulation spectrum relies on fitting with optical absorption of the materials where optical effect in different device geometries might introduce large variation in the extracted values. Here, we demonstrate a systematic electromodulation study with various fitting approaches in both commonly adopted reflection and transmission device architectures. Strikingly, we have found that the previously ascribed continuum state threshold from the deviation between the measured and fitting results is questionable. Such deviation is found to be caused by the overlooked optical interference and electrorefraction effect. A generalized electromodulation model is proposed to incorporate the two effects, and the extracted Δp and Δu have excellent consistency in both reflection and transmission modes in all organic film thicknesses.

Research Area(s)

  • ELECTRIC-FIELD DISTRIBUTION, HETEROJUNCTION SOLAR-CELLS, ENERGY-LEVEL ALIGNMENT, ELECTROABSORPTION SPECTROSCOPY, DIPOLE-MOMENT, CHARGE SEPARATION, BAND-GAP, POLYMERS, STATES, ABSORPTION

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