Estimation of External and Internal Quantum Efficiency

As the extraction efficiency of light from a thin-film device is limited by Eq. (8), new device structures were proposed to enhance extraction efficiency.48 

we define external EL quantum efficiency j (ext) by the ratio of the number of emitter photons outside the device divided by the number of charge carriers injected into the device. The internal EL quantum efficiency is defined by the number of photons produced within a device divided by the number of 

FIGURE 2.3. A schematic representation of the elementary processes for charge carrier recombination, production of molecular excitons, emission, and external emission. 

Using the charge-balance factory y, the efficiency of production for singlet excitons Tjr, and the quantum efficiency of fluorescence / /, the internal quantum efficiency 

FIGURE 2.4. Current flow of holes and electrons injected and transported inside an organic layer. /A and Je are net hole and electron current density, respectively. J, is the component of recombination current density.. /, and J e correspond to the hole and electron current densities, respectively, without recombination. 

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