Control of Ga Distribution in Cu(In,Ga)Se2 Photovoltaic Absorber by Solid-State Selenizatoin of CuGa/In/Se/In/CuGa Stack

概要

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Among many key parameters required to obtain a record-efficiency Cu(In,Ga)Se2 (CIGS) cell, the band-gap of CIGS should have a double-graded profile in which the band-gap increases toward both of the back and front of the absorber. In an effort to obtain an increased Ga content near the junction area which will raise the band-gap energy of CIGS, a novel metal precursor layered with predetermined amount of Se was annealed in N2 ambient. By inserting the Se layer in between metallic precursor layers, it was found that the front band-gap was increased due to the high Ga content by changing the direction of selenization reaction from inside to outside of metallic precursor. The proposed method is expected to provide a simple process for high quality CIGS photovoltaic absorber layer. The conversion efficiency of 6.80% with J_{\text{sc}} = 37.65 mA/cm2, V_{\text{oc}} = 0.51 V, and \mathrm{FF}= 35.4% in an active area of 0.48 cm2 was achieved.
2012-10-25