Photovoltage decay in p-n junction solar cells including the effects of recombinations in the emitter

Abstract

The expressions for the open circuit photovoltage decay in a p-n junction solar cell are derived, including the effects of recombinations in the emitter. It is shown that for a cell with base thickness wB≫LB, the base diffusion length, the voltage decay rate for small values of time depends on the emitter dark saturation current JE0; the larger the value of JE0 , the faster is the initial rate of voltage decay. For large values of time, the rate of voltage decay is solely determined by the minority carrier lifetime in the base τB and is independent of JE0 . However, for a cell with wB≲LB, the voltage decay is linear from the very beginning and the decay rate is of the form (kT/e)[(1/τB) +(1/t1)]. The time constant t1 is independent of τB . It, however, depends on the base thickness, the effective back surface recombination velocity, and the emitter dark saturation current JE0 . The value of JE0 depends on emitter thickness, front surface recombination velocity, drift field in the emitter, band-gap narrowing, and Auger recombinations in the emitter.

Open-circuit voltage decay transient in dislocation-engineered Si p–n junction

“…To our knowledge this is the first study of the open-circuit voltage decay transient in DE Si and we demonstrated the possibility of exponential decay of V oc (t). However, the results in figure 2 are different from those observed in some dislocation-free solar cells with a linear decrease in V oc (t) after the illumination is switched off [21][22][23][24]:…”

“…It is found [11][12][13][14][15][16][17] that V oc can decay according to the exponential function. However, in some dislocation-free solar cells V oc is found [21][22][23][24] to decrease linearly with time after the illumination is switched off.…”

Detailed analysis of the factors affecting emitter recombination in solar cells through the small-signal voltage decay method

“…One straightforward and elegant approach to the p-n coupling problem has been used by Jain and his co-workers [ 5 ] , [6]. Their approach, known as the Quasi-Static Emitter (QSE) approach is based on the assumption that the emitter is essentially in steady state during the voltage decay phase.…”