Pin junction photovoltaic element having an I-type semiconductor layer with a plurality of regions having different graded band gaps

Abstract

A pin junction photovoltaic element having an i-type semiconductor layer formed of a variable band gap semiconductor material, said i-type semiconductor layer being positioned between a p-type semiconductor layer having a band gap wider than that of said i-type semiconductor layer and an n-type semiconductor layer having a band gap wider than that of said i-type semiconductor layer, characterized in that said i-type semiconductor layer contains a first region (a) which is positioned on the side of said p-type semiconductor layer and also has a graded band gap, a second region (b) which is adjacent to said first region (a) and has a graded band gap, and a third region (c) which is positioned on the side of said n-type semiconductor layer and also has a graded band gap; said i-type semiconductor layer having a minimum band gap at the boundary between said first region (a) and said second region (b); the thickness of said first region (a) being less than one-half of the total thickness of said i-type semiconductor layer; and the gradient of the band gap of said third region (c) being greater than that of the band gap of said second region (b).

Dependencies are inferred from the claim text.