ITO-free top emitting organic light emitting diodes with enhanced light out-coupling

Abstract

Bottom emitting organic light emitting diodes (OLEDs) can suffer from lower external quantum efficiencies (EQE) due to inefficient out-coupling of the generated light. Herein, it is demonstrated that the current efficiency and EQE of red, yellow, and blue fluorescent single layer polymer OLEDs is significantly enhanced when a MoO x (5 nm)/Ag(10 nm)/MoO x (40 nm) stack is used as the transparent anode in a top emitting OLED structure. A maximum current efficiency and EQE of 21.2 cd/A and 6.7%, respectively, was achieved for a yellow OLED, while a blue OLED achieved a maximum of 16.5 cd/A and 10.1%, respectively. The increase in light out-coupling from the topemitting OLEDs led to increase in efficiency by a factor of up to 2.2 relative to the optimised bottom emitting devices, which is the best out-coupling reported using solution processed polymers in a simple architecture and a significant step forward for their use in large area lighting and displays.

Effect of thermal annealing Super Yellow emissive layer on efficiency of OLEDs

“…This is related to the changes observed in thermal and optical properties upon annealing Super Yellow. Efficiency of an OLED is dependent on PL efficiency3 and our results show that the PL intensities of Super Yellow films decreased for annealed films. The reduction in PL intensity is directly related to the degradation of polymer with annealing temperature.…”

“…High colour contrast1, flexibility2, wide viewing angles3 and printability4 make OLEDs highly desirable for display technologies such as screens for mobile phones and curved TVs. OLED is also an upcoming technology for solid state lighting5, since it can provide uniform illumination over a large area6 and offers the possibility for complex lighting designs and patterns.…”

“…Among solution-processable conjugated polymer emissive layers, copolymer Super Yellow is one of the most widely used emissive layers in organic light emitting devices including OLEDs316171819. It has been shown that different solution processing techniques for fabricating Super Yellow thin films have limited influence on its photophyical and charge transporting properties20.…”

Spontaneous Silver Doping and Surface Passivation of CsPbI3 Perovskite Active Layer Enable Light-Emitting Devices with an External Quantum Efficiency of 11.2%

“…Metal films are highly conductive but inherently opaque to visible light; therefore, when using them as transparent electrodes, the layer thickness should be low (typically less than 20 nm) to ensure transparency. 21 Metal oxide/metal/metal oxide trilayer structures, on the other hand, are widely employed in LEDs for achieving both high transparency and low resistance. 22 We thus tested different configurations of the cathode and anode trilayers to ensure the fulfillment of the above-mentioned conditions.…”

Nanophotonics-enabled smart windows, buildings and wearables

“…Visible transparency preserves design colors. Oxide/Ag/oxide stacks can be deposited at low temperature as needed for coating most threads or on a completed textile cloth and have already been demonstrated on thin polyester layers of poly(ethylene terephthalate) and poly(ethylene naphthalate) [82,91]. Another attraction of such stacks is they can also conduct.…”