Patent ID: 8227689
Filing Date: 2012-07-24
Classification: H01L,Y02E,Y02P

Abstract:
1. A solar cell comprising: a first layer having a first-layer lattice parameter; a second layer having a second-layer lattice parameter different from the first-layer lattice parameter, wherein the second layer includes a photoactive second-layer material; a third layer having a third-layer lattice parameter different from the second-layer lattice parameter, wherein the third layer includes a photoactive third-layer material; a graded first buffer layer extending between and contacting the first layer and the second layer; and a transparent graded second buffer layer extending between and contacting the second layer and the third layer and having a second-buffer-layer lattice parameter that decreases with increasing distance from the second layer toward the third layer; wherein the first layer is selected from the group consisting of Ge and GaAs; and wherein the second layer and the third layer are composed of one or more semiconductors selected from the group consisting of GaAs, GaInAs, GaInP, AlGaInP, AlGaInAs, GaInPAs; and wherein the first layer is a nonphotoactive substrate, the first layer positioned furthest from an incident light source defining a bottom-most layer of the solar cell; and wherein the second layer and third layer are subcells.