The dark current of the LED is the effective current where this current causes of injection of mobile carriers in the I-region from the end emitter regions.The injected charges recombine in the i-layer and emit light. So, one wants to enhance this recombination rate to increase production of light.

In the solar cell the dark current density must be made as small as possible at it is a lost current in the solar cells. One one to minimize it.

However both currents can be expressed by a Shockley like equation for the p-n junction as:Jd= Js exp V/nVt with Is is the reverse saturation current, n is the ideality factor and Js the reverse saturation cu-rent density.

One would like to make Is large for LED and small for SCs.

Best wishes

Thank you Prof. Zekry.