The effect of trap density on the trapping and de-trapping processes in determining the turn-on voltage of double-carrier organic light-emitting devices (OLEDs)
Document Type
Article
Publication Date
8-1-2021
Abstract
A double-carrier organic light-emitting device consisting of tris(8-hydroxyquinoline) aluminum (III) -(Alq(3)) as the emissive layer (OLED A) is fabricated. The trap density value obtained at voltage of 14 V when the device luminesces is 2.40 x-10(15) cm(-3). The rates of the capturing process (trapping) R-n and de-trapping, R-n' of the charge carriers on the localized state of the double-carrier device are estimated. There are two significant regions observed in the plot, R-n > R-n and R-n < R-n', and the intersection point of R-n with that of R-n' indicates the voltage at which the device luminesces, known as the turn-on voltage of the device. Simulations are then performed by directly increasing the device trap density by various ratios to that of OLED A. The simulation has indicated that trap density has a strong influence on the R-n and R-n' parameters. In order to verify the finding of the simulation, another double-carrier device (OLED B) with a hole transport layer (HTL) of poly(N,N'-bis-4 butyl phenyl-N,N'-bisphenyl) benzidine (poly-TPD) of 40-nm thickness is fabricated by adding the HTL layer to the existing structure of OLED A. The photoelectric characteristics analysis is performed on both types of OLED A and B. In this work, OLED B proved to have a higher value of trap density luminescence at a much lower turn-on voltage, as has been predicted by the simulation results due to the influence of trap density on the parameters R-n and R-n' of the devices.
Keywords
OLED, Alq(3), Trap density, Charge carrier transport
Divisions
PHYSICS
Funders
University of Malaya under the UMRG (RP026B-15AFR) (RP038D-17AFR),Postgraduate Research Fund (PG107-2015A)
Publication Title
Journal of Electronic Materials
Volume
50
Issue
8
Publisher
Springer
Publisher Location
ONE NEW YORK PLAZA, SUITE 4600, NEW YORK, NY, UNITED STATES