Influence of stoichiometry and temperature on quasi Fermi level splitting of sulfide CIS absorber layers

CuInS
₂
-based solar cells suffer from a low open circuit voltage. Absorbers grown under both Cu-excess and Cudeficiency have been used to fabricate record efficiency photovoltaic cells. In this work, we present the influence of stoichiometry on the quality of absorbers by means of calibrated room temperature photoluminescence and quasi Fermi level splitting evaluation (qFLs). Deep defects-related photoluminescence decreases using higher Cu/In ratio, leading to a corresponding improvement in qFLs, with values above 900 meV for high copper rich absorbers.