Comparison of MgCl2and CdCl2 Activation Treatment for CDTE Solar Cells: Recrystallization and Defects

One of the key factors for the success of CdTe solar cells is the so-called “activation” treatment, consisting in depositing a CdCl
₂
film on the CdTe layer and subsequent annealing it in air. Recent studies have found MgCl
₂
as a good alternative. In this work we have studied devices (exceeding 14% efficiency) prepared by low-substrate temperature CdTe deposition and activated with MgCl
₂
treatment (applied by wet deposition). The CdTe films recrystallized by MgCl
₂
were analyzed in terms of X-ray diffraction, atomic force microscopy, photoluminescence measurement and compared with the standard CdCl
₂
treated CdTe cells. Results show that different defects are detected for MgCl
₂
treated sample. Moreover MgCl
₂
treated cell does not need a post deposition treatment of the back contact to deliver high current density, showing that different electrical properties of the CdTe are registered.