Comparison of polycrystalline Cu(In,Ga)Se2 device efficiency with junction depth and interfacial structure

Abstract
X‐ray photoemission spectroscopy (XPS) and positron annihilation spectroscopy (PAS) have been used to characterize the surface versus bulk composition, electronic, and physical structure of polycrystalline Cu(In,Ga)Se2 thin‐film interfaces. Angle‐resolved high‐resolution photoemission measurements on the valence‐band electronic structure and Cu 2p, In 3d, Ga 2p, and Se 3d core lines were used to evaluate the surface and near surface chemistry of CuInSe2 and Cu(In,Ga)Se2 device grade thin films. XPS compositional depth profiles were also acquired from the near surface region. PAS was used as a nondestructive, depth‐sensitive probe for open‐volume‐type defects. Results of these measurements are related to device efficiencies to show the effects of compositional variations and defect concentrations in the near surface region on device performance.