Advances in continuous, in-line processing of stable CdS/CdTe devices

A continuous, in-line process suitable for large volume manufacturing of CdS/CdTe photovoltaic (PV) devices has been demonstrated at the pilot scale level. The pilot scale system incorporates the steps of glass heating, all semiconductor depositions, chloride heat treatment and ohmic contact formation in one chamber operating at modest vacuum. The cycle time is 2 minutes. The process is scaleable, uniform and reproducible. Utilizing this process, devices with efficiencies greater than 12% (verified at NREL) are repeatedly fabricated on unmodified Pilkington TEC 15 substrates without anti-reflection coatings. The stability of the devices is very promising. Many devices are being tested outdoors for stability. Outdoor results are compared to indoor stress testing. Detailed analyses of the novel copper based ohmic contact using X-ray photoelectron spectroscopy (XPS) and glancing angle X-ray diffraction (GAXRD) are presented.