Dark current transients in thin-film CdTe solar cells

Dark current transients measured by changing the voltage bias in a stepwise fashion on CdTe cells results in minutes-long transients after each step. Transients measured at room temperature are controlled by carrier trapping that corresponds to the well known voltage transient phenomena. Transients measured on the same CdTe cell at elevated temperature (60°C and 90°C) show the emergence of a second much slower process. We associate this second process with "shunt" current paths induced by reverse bias and removed with forward bias. A different back contact process may produce an opposite voltage dependence. The lack of these transients may be required for the fabrication of "stable" thin-film CdTe solar cells.