The invention of an improved Nanotech OLED electrode

Akash Singh, Banaras Hindu University

An organic light-emitting diode (commonly abbreviated as OLED electrode) or organic LED is defined as a light-emitting diode. The emissive electroluminescent layer in it is a film of organic compound that emits light in response to an electric current. It was created in response to the need for more energy-efficient displays, and as a result, it was extremely energy-efficient and had a reduced theoretical manufacturing cost. The University of Michigan has submitted a patent for an upgraded OLED that might release up to 20% more light. The invention of this improved nanotech OLED electrode will be more power-efficient than conventional OLEDs.

Quantum efficiency (QE):

It is a measurement of an imaging device’s ability to convert incident photons into electrons. When exposed to 100 photons, a QE of 100% means that the gadget will produce 100 electrons of signals. Internal quantum efficiency (IQE) and external quantum efficiency (EQE) are two types of quantum efficiency (EQE). With the help of phosphorescent molecules containing metal complexes and thermally activated delayed fluorescence molecules with a narrow singlet and triplet energy gaps, OLEDs attain 100% IQE. However, without any out-coupling structure on a glass substrate, the EQE of OLEDs is restricted to roughly 20%.

Factors that limit External Quantum Efficiency (EQE) of OLEDs:

1. Due to stimulation of the surface plasmon-polariton (SPP) mode, a portion of the photons generated by the emissive layer (EML) is lost at the interface between contact metal and organic stacks.
2. Due to 100% internal reflection at the air/substrate interface, light is trapped in the substrate and cannot escape the device.
3. Because the organic stacks and transparent conducting electrodes (TCE) operate as a waveguide, light created at the EML is trapped inside the OLED as propagating mode.

Strategies to counter the limitations:

In OLEDs, low index grids, gratings, buckling patterns, reactive ion etching-induced nanostructures, and corrugated structures have all been used to out couple light trapped in the waveguide mode in the previous decade. In fact, there has been a lot of study towards extracting trapped light at the substrate, and there are now feasible methods, but liberating trapped and lost light in the SPP and waveguide modes remains a challenge. Using a thick electron transport layer (ETL), where the energy wasted to SPP is significantly reduced but a higher amount of light energy resides in the waveguide mode, is one effective way to avoid such energy loss. As a result, to achieve high EQE light trapped in the waveguide must be liberated.

Increasing EQE by using ultrathin Ag film-based OLED:

Waveguide mode may be fully avoided by optimizing the organic stacks and employing ultrathin Ag anodes, according to Changyeong Jeong and colleagues’ research. They claim that this technique is compatible with commonly used manufacturing processes and improves OLED EQE without affecting other device properties.

The process for reducing waveguide mode is revealed by their model analysis. The waveguide modes are below the cutoff thickness due to the Ag anode’s intrinsic negative permittivity and exceedingly thin thickness. As a result, the waveguide modes are not supported by the standard organic layer thickness employed in OLEDs, resulting in significantly increased EQE. Their approach helps to improve light output efficiency and EQE by introducing a mode removal mechanism.

Prospects:

Natural resources on the planet are limited, and every technological innovation revolves around this fact. The only way to thrive in an environment where resources are scarce and consumers expand by several folds every year is to create optimized devices that can preserve more energy. Energy-efficient devices are the future. This research model will help us to reduce 20% energy wastage by an OLED electrode by increasing the EQE by 20%. “By substituting our nanoscale layer of transparent silver for typical indium tin oxide electrodes, the industry may be able to liberate more than 40% of the light,” said Changyeong Jeong, first author and PhD candidate in electrical and computer engineering. They now want to apply their modal elimination method to other solid-state LEDs such as perovskites, quantum dots, and III-V-based LEDs, which are all susceptible to light trapping as a waveguide mode. With well-optimized, energy-efficient equipment, this research has undoubtedly established the groundwork for a better future.

Also read: Nanotechnology for pain management

References:

1. Jeong, C., Park, Y., & Guo, L. (2021). Tackling light trapping in organic light-emitting diodes by complete elimination of waveguide modes. Science Advances, 7(26), eabg0355. https://doi.org/10.1126/sciadv.abg0355
2. Li, Y., Kovačič, M., Westphalen, J. et al. Tailor-made nanostructures bridging chaos and order for highly efficient white organic light-emitting diodes. Nat Commun 10, 2972 (2019). https://doi.org/10.1038/s41467-019-11032-z

About author:

Akash Singh is a first year masters student of Biochemistry in Banaras Hindu University. He plans to pursue a PhD in the future. He aims to research and teach the young minds of the country.

Social media links: LinkedIn: https://www.linkedin.com/in/akash-singh-82b5811a2/

Publications :

1. https://vidwaanforever.com/2021/06/a-new-period-invention-a-novel-thread-device-for-uti-detection/
2. https://vidwaanforever.com/2021/06/the-fall-of-insecta-apocalyptic-consequences-for-humanitys-survival/
3. https://vidwaanforever.com/2021/06/covaxin-vs-covishield-the-corona-vaccines-in-india/ 

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