Light-induced increase in the open-circuit voltage of thin-film heterogeneous silicon solar cells

We observe a significant light-induced increase in open-circuit voltage, $V_{\mathrm{oc}},$ of solar cells whose intrinsic $\mathrm{(i)}$ layer consists of an amorphous and microcrystalline mixed phase. The increase depends on the $i$ -layer thickness and light-soaking intensity. An increase of as large as 150 mV or 20% of the original $V_{\mathrm{oc}}$ is observed. The original $V_{\mathrm{oc}}$ is restored after subsequent thermal annealing. The possible mechanism for the $V_{\mathrm{oc}}$ increase is discussed.