The effects of pressure on the fabrication of CdS/CdTe thin film solar cells made via pulsed laser deposition

CdS/CdTe thin film solar cells with 100 nm CdS and 1.0-1.5 μm CdTe have been made in situ using pulsed laser deposition (PLD). This work intends to investigate the effect of PLD chamber pressure on the CdTe absorber layer. In particular, a comparison between two specific cases of Ar at 8% of O₂ and pure O₂ was made to elucidate the role of O₂ and Ar in formation and physical properties of the CdTe absorber. At the same O₂ partial pressure of 1.2 torr, an efficiency of 6.4% was obtained in the latter case, which represents a considerable improvement over the former case with the best efficiency of 6.7% previously reported which utilized a 1.5 μm CdTe layer. This result suggests that the availability of oxygen near the growing CdTe film is important during PLD of CdTe layers and the better performance in PLD of CdTe in pure O₂ may be attributed to the more preserved kinetic energy of the reaction species due to the reduced total gas pressure.