Effect of <i>p</i>/<i>i</i> interface layer on dark <i>J</i>-<i>V</i> characteristics and <i>V</i>oc in <i>p</i>-<i>i</i>-<i>n</i> <i>a</i>-Si solar cells

Abstract

Dark current-voltage (J-V) characteristics of p-i-n a-Si solar cells are studied to clarify the effect of the p/i interface layer on the open-circuit voltage (Voc). It is shown that the recombination current in the p/i interface region is predominant in the a-Si solar cells with an i-layer thickness of less than 200 nm and has a great effect on the dark-current transport in the solar cells. It is also shown that the current transport of the cells with the p/i interface layer of constant band gap of a thickness of more than 14 nm is effectively the same as that of a cell in which the band gap of the whole i layer is equal to that of the interface layer. A model in which the dark current of the cell consists of the recombination current at the p/i interface and the recombination current in the bulk region of the i layer is proposed. Using this model, the Voc degradation for the a-Si solar cells with the p/i interface layer is shown to be due to the defects generated in the i layer.