Study of MgCl2 activation treatment on the defects of CdTe solar cells by capacitance-voltage, drive level capacitance profiling and admittance spectroscopy techniques

In this work we have studied devices (exceeding 14% efficiency) prepared by low-substrate temperature CdTe deposition and activated with MgCl2 treatment (applied by wet deposition). The devices were characterized by means of current-voltage, capacitance-voltage, drive level capacitance profiling and admittance spectroscopy techniques. Carrier concentration and also concentration and distribution of shallow and deep defects are presented and compared with data obtained from analogous devices but activated with the standard CdCl2. Despite CdTe layers treated with the two different processes exhibit similar structural properties, the distribution of deep and shallow defects results to be different and moreover admittance spectroscopy technique reveals the presence of different defects, at 344 and 358 meV, which are present only in MgCl2 treatment case.