I have fabricated an all-inorganic QLED with FTO/NiO/CdSeZns/ZnO/Al. It has three conduction regions corresponding to Ohmic, Trap limited and space charge limited (SCLC). I expect the device to emit efficiently in the trap limited region and saturate in the SCLC region. But, the device emits efficiently in the SCLC region. Is there an explanation to this? Attached is the plot of current density and luminance (cd/m2) as a function of voltage.
Dear Ramesh,
I order to interpret the results correctly, you have to plot the emitted light intensity as a function of voltage in a logarithmic scale also. And then you have to plot the emitted light intensity as a function of current density rather. It is the matter of the excess electrons and holes prevailing in the active region and how they change with current flowing in the device. The dependence of the current on the voltage depends on current conduction mechanism.
After making the required plots we will have better look at the device.
Best wishes
Following my post above, an important question is that what do you mean by radiation efficiency? Is it the output radiation power Prad divided the input power Pin, which is equal to Pin= I V.
I meant the quantum efficiency (photon flux density/electron flux density) here.
The electron flux density is= J/ q, where J is the current density and Q is the electronic charge, while the photon flux density is radiated optical power density per photon energy Eph.
So this quantity is proportional to the Lumenance divided by the current density. So, the best representation of the required function is to plot the lumenance versus current density in a linear scale.
The slope will be an indication of the required efficiency.
Best wishes
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