Measurement of shunt resistance and conduction band offset in Cu(In, Ga)Se₂ solar cells through joint analysis of temperature and intensity dependence of open-circuit voltage and photoluminescence

Joint analysis studies of open-circuit voltage and photoluminescence intensity (PL-I) are reported for CuIn_1-xGa_xSe₂ (CIGSe) solar cells. A range of compositions are investigated, including constant x = 0.35 and x = 0.55 as well as a graded composition profile having a minimum of x = 0.25. Both the open-circuit voltage and PL-I are measured as functions of temperature and illumination intensity. With these two measurements, a full model-based fitting of the temperature and illumination dependence allows extraction of the effects of window layer band offset and shunt resistance, in addition to bulk and interface recombination parameters. To quantitatively analyze the two distinct measurements jointly, the absolute PL-I is measured to obtain quasi-Fermi-level splitting.