Large Area Cu(In,Ga)Se_2 Films and Devices on Flexible Substrates Made by Sputtering

摘要

A reactive sputtering process was developed for the production of Cu(In,Ga)Se_2 films on a moving stainless steel substrate, in simulation of the operation of a roll coater. Cu, In and Ga fluxes were provided through magnetron sputtering and were reacted in a flux of Se on the heated substrate. CdS films were deposited either by chemical bath deposition (CBD) or by sputtering. Devices of the type steel/Cr/Mo/CIGS/CdS/ZnO/Ag were completed by sputtering ZnO layers and by screen printing grid lines. We made devices with efficiency values above 9%. A uniformity study was performed on a CIGS film and on small area devices made from it. The target length was 12". Targets of this size are expected to produce a uniformly thick deposit over a range of 6-8". The film thickness was 2.54 μm over a range of 6" with a standard deviation σ of 0.04 μm. The film composition was uniform over a range of 16". The values of Cu/III and Ga/III were 0.84 and 0.31, with σ values of 0.02 and 0.01, respectively. The efficiency of all-sputtered devices was uniform over a range of 12", well beyond the 6" wide range of constant CIGS film thickness. Their efficiency was 6.6% on average with σ=0.6%.