Analyses on ZnO/CdS heterojunction for design of CIGS photovoltaic device with higher accuracy

In this work, ZnO films were prepared by atomic layer deposition (ALD) and CdS films were deposited using chemical bath deposition (CBD) to form a ZnO/CdS heterojunction in the Cu(In,Ga)Se₂ (CIGS) solar cell. More accurate mapping of band arrangement in the ZnO/CdS heterojunction has been performed by studying both its electrical and optical characteristics in depth by various analysis methods including transmittance, sheet resistivity measurement, and photoemission spectroscopies. Energy-band structures of the ZnO/CdS heterojunction could be accurately drawn from the extracted parameters taking the conduction band offset (CBO) into account. Consequently, a delicate description of the energy-band structure of the heterojunction has been made possible in this study, which would help acquisition of the full band structures of the thin films in the CIGS solar cell device and contribute to its reliable design with higher accuracy.