Influence of Slow Surface States on Effective Lifetime Measurements

In a recent work, the effect of surface states following a change of the Fermi level with a characteristic relaxation time τrelax on transient effective charge carrier lifetime measurements has been described. The working condition for solar cells, however, is a steady-state low-injection at the passivated surface. In the work presented here, the effect of such surface states in steady-state low-injection conditions is discussed and the considerations are compared with quasi-steady-state lifetime measurements on a sample exhibiting such surface states. Careful comparison of transient and quasi-steady-state lifetime measurements leads to an evaluation of the characteristic relaxation time of the surface traps.