The Determination of the Electronic Parameters of Thin Amorphous Organic Films by Ellipsometric and Spectrophotometric Study

Natalia Nosidlak,Piotr Dulian,Janusz Jaglarz,Dariusz Mierzwiński

doi:10.3390/coatings10100980

Natalia Nosidlak, Piotr Dulian + Show 2 more

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https://doi.org/10.3390/coatings10100980

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Journal: Coatings	Publication Date: Oct 14, 2020
Citations: 3	License type: CC BY 4.0

Affiliation: Cracow University of Technology, Institute of Physics

Abstract

The aim of this work was the determination of the basic optical parameters and electronic structure of conjugated polymer films by two commonly used techniques—spectrophotometry and ellipsometry. Poly(3-hexylthiophene (P3HT) and poly(3-octylthiophene (P3OT) conductive polymers films deposited on a glass substrate by the spin-coating technique showed very comparable surface structures composed of grains of similar sizes and shapes. X-ray tests confirmed that the polythiophene layers are amorphous, which confirmed the correctness of the choice of the optical models used. Selected optical models (Lorentz, Tauc–Lorentz and Cody–Lorentz) have been applied in order to determine the thickness, and optical parameters such as refractive index and extinction coefficient, absolute absorption and electronic parameters (energy gap Eg, amplitude A and broadening B). Spectral absorption determined from spectrophotometric measurement is similar to the absorption spectrum obtained from the ellipsometry method with the application of oscillator models.

Highlights

For many years, conjugated polymers have been the subject of interest of many scientists in the field of organic semiconductors
We present the usefulness of the models described in the literature to determine the optical parameters of poly(3-hexylthiophene (P3HT) and poly(3-octylthiophene (P3OT) layers deposited by the spin-coating method on glass and silicon substrates
The electro-optical properties of thin polymer films are closely related to surface morphology and the fabricated

Summary

Introduction

For many years, conjugated polymers have been the subject of interest of many scientists in the field of organic semiconductors. It is their optoelectronic properties that make them suitable to use in solid-state devices such as field effect transistors (FETs) [1,2], organic light emitting diodes (OLED) [3,4]. The unique optoelectronic properties of conjugated polymers are the result of the existence of π bonds in the electronic structure of the polymer. The optoelectronic properties of the π conjugated polymers are a function of their chemical nature, the spatial arrangement of the polymeric chain and film morphology. The polymer microstructure and film morphology are strongly dependent on the processing conditions

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