Progress in four-terminal nano-crystalline Si/amorphous Si solar cells

We report a conversion efficiency of /spl sim/9.5% using nano-crystalline Si/amorphous Si (nc-Si/a-Si) solar cells constructed in a four-terminal (4-T) tandem junction configuration. This type of tandem junction releases the constraint of current matching from each constituent cell thus allowing the fabrication of thin film Si stable, high efficiency devices. The improvement in efficiency, in comparison with our earlier results, is due to the use of MgF/sub 2/ anti-reflection (AR) coating which reduces the reflection loss at the ITO/air interface at the front portion of the entire device.