Improved efficiency and lifetime study of InP/CdS solar cells

The p-InP/n-CdS solar cell, made of inexpensive raw materials and chemically stable components, is a candidate for large scale applications. Cells with initial efficiencies between 8 and 12.5% (the previously reported maximum) are improved to 14% by a 15 minute anneal in 15% H2+ 85% N2at 550 to 600°C. The main effect of this anneal is to increase the open circuit voltage, VOC, to 0.72 V. We find that the cell characteristics do not change during 15 minute anneals in air up to 400°C. At higher temperatures VOCgoes up as in the forming gas anneals, but the conductivity of the CdS drops. Starting with these observations we have begun a lifetime study.