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

摘要

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).