Determination of the temperature dependency of the electrical parameters of CIGS solar cells

Two types of Cu(In,Ga)Se₂ (CIGS) solar cells, both designed for implementation in CIGS modules, were subjected to temperatures between 25C and 105C. Simultaneous exposure to AM1.5 illumination allowed the measurement of their electrical parameters at these temperatures. These two types of solar cells, produced with different deposition routes on soda lime glass (SLG) and polyimide (PI) substrates, showed large variations in the temperature dependency of their electrical parameters. It was shown that the temperature dependency of the open circuit voltage (V_oc) was dependent on its room temperature value: a high V_oc at 25 °C led to a slower loss of V_oc when the temperature was increased. For the V_oc, the normalised temperature dependency varied between -0.28%/°C and -0.47%/°C, which is in agreement with the literature. The temperature dependency of the short circuit current density (J_sc) showed more surprising results: while the PI samples had the expected positive temperature dependency (0.03 to 0.32%/°C), the SLG samples showed a small negative impact of increasing temperature (-0.01 to -0.05%/°C). A correlation between the temperature dependencies of the J_sc and the ideality factor n was observed. Therefore, this difference in the temperature dependence of the J_sc could be caused by increased recombination for the SLG samples. Furthermore, the temperature coefficients of the fill factor (negative), efficiency (negative), and the series (slightly negative) and shunt (negative) resistances were calculated.