CdTe-Based Thin Film Solar Cells: Present Status and Future Developments

CdTe solar cells are the most successful thin film photovoltaic technology of the last ten years. It was one of the first being brought into production together with amorphous silicon (already in the mid 90 s Solar Cells Inc. in USA, Antec Solar and BP Solar in Europe were producing 60 × 120 cm modules), and it is now the largest in production among thin film solar cells. CdTe solar cells stand out for the robustness of the absorber material: its high chemical stability and the large variety of successful preparation methods available make them suitable for large area module production. Compared to other thin film absorber materials, CdTe has an optimum band gap of 1.5 eV so that it could deliver efficiencies above 27%, with an open- circuit voltage of 1 V and a short-circuit current density of 30.5% mA/cm2. In this chapter, we will follow the history of the fabrication process together with each and every improvement explaining the discoveries and achievements that have brought to the record efficiency of 22.1%. Moreover, the environmental impact, the future applications and the possible evolutions of this technology will be also described.