Near surface defects: Cause of deficit between internal and external open‐circuit voltage in solar cells

Interface recombination in a complex multilayered thin-film solar structure causes disparity between the internal open-circuit voltage (VOC,in), measured by photoluminescence, and external (VOC,ex), that is, VOC deficit. Aspirations to reach higher VOC,ex values require comprehensive knowledge of connection deficit interface recombination. Here, near-surface defect model is developed for copper indium di-selenide cells grown under Cu-excess conditions. These cell show typical signatures recombination: strong VOC,in VOC,ex, extrapolation temperature dependent q·VOC,ex value below bandgap energy. Yet, these do not suffer from reduced or Fermi-level pinning. The presented based on experimental analysis admittance deep-level transient spectroscopy, which signature an acceptor defect. Numerical simulations using defects without need findings demonstrate measurements alone can be inconclusive might conceal information pathways, establishing complementary techniques like current–voltage identify cause devices.