Patent ID: 8987042
Filing Date: 2015-03-24
Classification: H01L,Y02E

Abstract:
1. A method of forming a multijunction solar cell comprising a top subcell, at least one middle subcell, and a bottom subcell, the method comprising: forming a semiconductor contact layer composed of GaAs over the top subcell; depositing a metal contact layer including a germanium layer having a thickness of 100 nm and a palladium layer having a thickness of 50 nm over the semiconductor contact layer; and forming an ohmic metal contact from the metal contact layer to the semiconductor contact layer at a temperature of 210 degrees C. or less, wherein the multijunction solar cell is a triple junction solar cell composed of III-V compound semiconductor material including the top subcell, the at least one middle subcell, and the bottom subcell, wherein the top subcell has a first band gap; the at least one middle subcell has a second band gap smaller than said first band gap; a graded interlayer is disposed over said at least one middle subcell that is compositionally graded to lattice match the at least one middle subcell on one side and the bottom subcell on the other side; the bottom subcell disposed over said graded interlayer has a fourth band gap smaller than said second band gap such that said bottom subcell is lattice mismatched with respect to said at least one middle subcell.