Recombination Efficiency in Bilayer Organic Light Emitting Diodes

Rishi Jaiswal; Lekhram Sahu; R.S.Singh; R.N.Baghel

Rishi Jaiswal SoS in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur, India.
Lekhram Sahu Department of Physics, Seth Phoolchand Agrawal Smriti College, Nawapara, India.
R.S.Singh Department of Physics, Government D.T. College, Utai, Durg, India.
R.N.Baghel SoS in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur, India.

Keywords: Recombination efficiency, Hole transporting layer, Electron transporting layer

Abstract

Bilayer Organic Light Emitting Diodes (OLEDs) consists of two thin organic layers sandwiched between two electrodes, with the structure, ITO (anode)/ hole transporting layer (HTL)/ electron transporting layer (ETL)/Al (cathode). In this paper we assume the analytical model and using the numerical simulations to calculate efficiency of carrier recombination in bilayer OLEDs. It is shown that the most important factor that determines efficiency is the ratio of hole and electron mobility in the ETL. When this ratio is much less than unity, recombination efficiency is 100% even without the presence of either an electron or hole barrier at the organicorganic interface. However, if the hole mobility is much higher than electron mobility, then a hole barrier at the organic interface is necessary to achieve a high recombination efficiency. The minimum interfacial hole barrier height required for high efficiency increases with the ratio of hole and electron mobilities in electron transport layer. The present study may be useful for the increasing recombination efficiency in bilayer OLEDs.

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