Fabrication of Zn1-xMgxO Buffer Layers for CIGS Solar Cells by Atomic Layer Deposition Using Mg(CpEt)2 as a Mg Source

Zn1-xMgxO thin films with wurzite structure were deposited by the ALD process using diethylzinc (Zn(C2H5)2) and bis-ethyl-cyclopentadienyl-magnesium (Mg(CpEt)2) as metal precursors and water vapor as a reactant. We confirmed that the bandgap energy of the Zn1-xMgxO films increase as Mg contents increases, and bandgap energy and chemical composition can be precisely controlled by MgO/ZnO cycle ratio. The CIGS solar cells using Zn1-xMgxO buffer layer showed 12.5% energy conversion efficiency. Based on these properties, we suggest that Zn1-xMgxO thin films deposited by ALD using Mg(CpEt)2 can be used as the buffer layer for Cu(In,Ga)Se2 solar cells.