Currently, I am studying the working of OLED devices! The device can work with just three layers which are Anode, Cathode and Emission layers. I know the fact that the work function is an important parameter in the device. I have read articles about Various layers which can we add in devices to increase the overall performance of the device.
The layers we add for improving efficiency are as follows
I know the fact that To overcome losses in devices, a step-wise energy transport architecture is used, and the work function of layers are in between the emission layer and electrodes.
My question is How those layers can help in increasing efficiency? Why do we use them? I need a detailed explanation of this question with proper work function values
Dear Prerna Gupta,
You mentioned one of the important key points to design an efficient OLED about energy alignments for each layer to overcome the barriers for charge carriers (either holes or electrons) transport and meet within the emitters, generating photons which have light out from a device.
There are several other key points for an efficient OLED, too.
Firstly, charge carrier mobilities in organic semiconductors are very low compare with the counter semiconductors of silicon. The mechanism of charge carrier transport in organic semiconductor is very different from inorganic semiconductors. There are many references easily found.
Secondly balancing electrons and holes within the organic emitter in on OLED device is crucial for operating stable devices. In another words, lifetime of a device is the foundation of commercialisation or applications.
If you look back how an OLED was invented in the history, there was a single layer device used in 1960s or 1980s. However, there have been decades of effort from scientists and engineers to achieve today's OLED products via multi-layers device structures. The reason behind is to have so many different materials design and synthesis, materials characteristics, device structure design and engineering.
Some books are recommended in the following
https://www.amazon.co.uk/OLED-Fundamentals-Materials-Processing-Light-Emitting/dp/146651518X
https://onlinelibrary.wiley.com/doi/book/10.1002/9781119040477
Dear Gupta,
In OLED different layers, ETL is the electron transport layer, EMLis emissive layer, HTL is the hole transport layer. we can
inter HML layer between HTL/EML and EML/ETL to increase the holes rate injected into the recombination zone and the transport layer works to increase the charge carriers to the emission layer and increase efficiency.
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