Dear Prerna Gupta,

Firstly, there are many books and publications regarding the mechanism of OLEDs, which you could find it easily.

In summary, the low work function cathode is aligned to the election injection or transport layer of OLEDs. The high work function anode is used for hole injection of OLEDs. The multi-layers of OLED have to satisfy the essential conditions to achieve high efficiency and long life span of OLED devices to achieve the stage of commercial products.

I include the following references

https://en.wikipedia.org/wiki/OLED

https://www.elsevier.com/books/principles-and-applications-of-organic-light-emitting-diodes-oleds/thejo-kalyani/978-0-08-101213-0

Hello Prema,

Generally, a OLED is a LED. The D means diode. If you want to create luminescence, you must generate excess carriers. This can you do by excitation with light - laser excitation. The recombining excess carrier then give luminescence (or no radiative processes like Auger recombination). In this case you only need a n or 9-material.

In the case of a diode you inject carrier from n- to p-material and vice verca. A diode is a valve for electrons and holes. In the thermal equilibrium you have a potential difference between n and p region. This is connected with an electric field. This is often used to realize photo diodes (solar cells). If you apply a voltage, the potential difference is reduced (or enhanced in the case of wrong polarity). Now electrons can flow from n+ into n- region and from p+ to p-.

There the electrons or holes are excess carrier and recombinant. The energy is delivered from the outer voltage source. That this works, the energy level between n and p region must be equalized. Here, the work functions are important.

With Regard

Rüdiger Mitdank

A reflective anode and a transparent (or more often semi-transparent) cathode are used so that the light emits from the cathode side, and this configuration is called top-emission OLED (TE-OLED). So, both are must be needed.