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.