Transient lifetime measurements rely on the decay of carriers over time. Carriers are generated by a very short pulse of light and the decay of the carrier density with time is measured. The longer the minority carrier lifetime the more slowly the carriers decay.
Illumination time and minority carrier density. The pulse of light is very short and the carrier density typically follows an exponential decay. Move the mouse over the graph to see that the carrier density decay is a straight line on a log scale.
Minority carrier lifetime: 0.001 seconds
In the animation above the slider controls the minority carrier lifetime. Increasing the lifetime causes the carriers to decay more slowly.
which leads to the final relation between lifetime and excess carrier density
Minority-Carrier Lifetime (no Auger correction) vs. Carrier Density