High band gap Cu(In,Ga)Se2 solar cells and modules prepared with in-line co-evaporation

Cu(In1-xGax)Se-2 thin film solar cells were prepared with our standard in-line deposition process with x = 0.3, 0.68 and 1. The devices with x > 0.3 reach a lower efficiency compared to the standard device with x = 0.3 due to the increasing difference between the band gap energy E-g and the open circuit voltage V-oc. The current-voltage characteristics under illumination show an increasing slope at zero bias with increasing Ga content, indicating an increasing voltage dependence of current collection. The temperature dependence of the photovoltaic output parameters is discussed in respect to whether the wide gap devices could reach higher efficiencies than the standard devices at high temperatures. The influence of chemical bath deposition process parameters is investigated. The time the absorber is exposed to the atmosphere before chemical bath deposition is found to become more important with increasing Ga content of the absorber. (C) 2003 Elsevier Science B.V. All rights reserved.