Thin film solar cell with graded bandgap structure

Abstract

A thin film solar cell with a graded bandgap structure comprises a front contact, a first light absorption layer, a transition layer, a second light absorption layer and a back contact. The first light absorption layer is formed on the front contact, the transition layer is formed on the first light absorption layer, the second light absorption layer is formed on the transition layer, and the back contact is formed on the second light absorption layer, wherein the transition layer has a graded bandgap, which is made by alternating a layer of the first superlattice layers, having a first bandgap, with a layer of the second superlattice layers, having a second bandgap, in a tandem arrangement, based on the condition that the thickness of each layer of the first and the second superlattice layers is varied increasing, decreasing or increasing first and then decreasing.