Abstract
Organic light-emitting diodes are generally depicted as sequential deposition of active layers and electrodes onto a substrate, but commercial devices are fabricated using pixellization technique, where an insulator layer is introduced between the indium tin oxide and organic layer to define the area of the active device. Here, we have inserted a layer of photoresist (thickness ~ 200 nm) at the edge of patterned anode (indium tin oxide) and between the anode and hole transport layer (Poly 3, 4-ethylenedioxythiophene poly styrenesulfonate) to examine its effect on the leakage current of organic light-emitting diode and on the electron-hole recombination ratio in the emission area, as a result increasing the luminance efficiency. Current leakage causes the loss of charges, which adversely affects the recombination of electrons and holes in the emitting zone and results in poorer luminance efficiency. In this paper, we report the effect of pixellization on current density-voltage, luminescence-voltage and degradation behavior of single layer Poly[2-methoxy-5-(2’-ethylhexyloxy)-1, phenylene vinylene] based organic light-emitting diodes. Devices with isolation layer have 30% higher external electroluminescence quantum efficiency and reduced device degradation in comparison to without isolation layer.
Highlights
Application of organic light-emitting diodes (OLEDs) in flat-panel and flexible displays requires development of processing technology
Organic light-emitting diodes are generally depicted as sequential deposition of active layers and electrodes onto a substrate, but commercial devices are fabricated using pixellization technique, where an insulator layer is introduced between the indium tin oxide and organic layer to define the area of the active device
We have inserted a layer of photoresist at the edge of patterned anode and between the anode and hole transport layer (Poly 3, 4-ethylenedioxythiophene poly styrenesulfonate) to examine its effect on the leakage current of organic light-emitting diode and on the electron-hole recombination ratio in the emission area, as a result increasing the luminance efficiency
Summary
Application of organic light-emitting diodes (OLEDs) in flat-panel and flexible displays requires development of processing technology. High local Joule heating by high local currents causes interdiffusion at the hole transport layer/electron transport layer (HTL/ETL) interface and leads to a reduction of currents in the mixed area [15]. These have been identified as causes of device instability. In this study we insert, a layer of photo-resist, between the patterned ITO and cathode to explore its effect on the leakage current of OLEDs and on the electron-hole recombination in the emission area, and its effect on Luminance. The stability is improved due to combined effect of reduced leakage and electric field at the edges of ITO by using isolation layer
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