Diffusion-Controlled Currents DCC

It is identical with Eq. (168a) except for the mobility which in the double-injection case is a complex combination of individual electron ( e) and hole ( h) mobilities, including so called recombination mobility (po), 

Let us note that the introduction of (io accounts for the recombination effect on the current. Its relation to the carrier 

An organic LED operating under such conditions should show emission from the entire emitter bulk as the recombination occurs on the total carriers paths equal to the emitter thickness, d. The recombination zone width w d (see Sec. 3.3). 

the requirement of high values of the electron-hole recombination coefficient requires double injection from two Ohmic contacts to produce two SCL currents meeting and annihilating each other somewhere in the emitter within a narrow recombination zone (w rf). 

It is interesting to note that in the Langevin recombination mechanism with the yeh expressed by the sum of the individual carrier mobilities (4), the interrelation between z/e,h and po switches to the relations between electron and hole 

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