Optical Properties of Alq 3 /TiO 2 BDR Structure Processed by Spin Coating Technique
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.22
Optical Properties of Alq3/TiO2 BDR Structure Processed by Spin Coating Technique L. Ajith DeSilva1,2*, Sarahn Nazaret1, A. G. U. Perera2, T. M. W. J. Bandara3 1
Department of Physics, University of West Georgia, Carrollton, GA 30118, USA
2
Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 USA
3
Department of Physics, University of Peradeniya, Peradeniya, Sri Lanka
*
corresponding author: [email protected]
ABSTRACT
One-dimensional hybrid Distributed Bragg Reflector (DBR) is constructed using Tris (8hydroxy) quinoline aluminum (Alq3) molecules and Titanium dioxide (TiO2) nanoparticles via spin coating process. Light emission from thin films of low molecular weight organic semiconductor of Alq3 is dominated by excitons. This material has been widely used as a superior emitter for organic light emitting diodes. Titanium dioxide (TiO2) is an inorganic semiconductor with a high band gap. Photoluminescence (PL) of thin films of Alq3 showed a broad PL peak at 530 nm. In DBR structures, PL quenching is observed but there is no shift in the PL peak of the Alq3. The PL quenching is tentatively attributed to energy transfer via sensitization to wide band gap TiO2 layers. A simple excitonic model is suggested to explain the observation. Fabrication process and optical properties of the structure are presented.
1. INTRODUCTION During the past decade, small molecular based organic semiconductors have attracted a lot of interest because of their versatility in both research and technologies [1, 2]. Some examples for promising applications include organic light emitting diodes (OLED’s), solar cells, field effect transistors, photodetectors, and organic lasers [2-5]. However inorganic counterpart has excelled for decades in most commercial products
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due to their superior qualities such as speed and durability. The organic materials possess the advantages of flexibility, lightness, and low cost while inorganic semiconductors still have the edged for higher charge carrier mobility and low dielectric breakdown. In particular inorganic semiconducting nanoparticles also known as quantum dots exhibit the properties of atoms and molecules. Colloidal quantum dots are chemically made suspended nanoparticles in a solution. They are easy to handle when implanting into devices and their properties can be tuned for desired applications. Both organic molecules and inorganic nanoparticles can be processed in solutions and deposited by low temperature processes such as sol-gel processing, spin coating and dip coating or screen printing. Amongst these techniques, spin coating is probably the most reliable, consistent and low-cost method to make controlled thin films [6]. A distributed Bragg reflector (D
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