High Efficiency Narrow Gap and Tandem Junction Devices: Final Technical Report, 1 May 2002--31 October 2004

The work described in this report uses a modified pulsed plasma-enhanced chemical vapor deposition (PECVD) technique that has been successfully developed to fabricate state-of-the-art nc-Si materials and devices. Specifically, we have achieved the following benchmarks: nc SiH device with an efficiency of 8% achieved at a deposition rate of~1 A/s; nc SiH device with an efficiency of 7% achievedat a depostion rate of~5 A/s; large-area technology developed using pulsed PECVD with uniformity of +/-5% over 25 cm x 35 cm; devices have been fabricated in the large-area system (part of Phase 3); an innovative stable four-terminal (4-T) tandem-junction device of h> 9% fabricated. (Note that the 4-T device was fabricated with existing technology base and with further development can reachstabilized h of 12%); and with improvement in Voc~650 mV, from the current value of 480 mV can lead to stable 4-T device with h>16%. Toward this objective, modified pulsed PECVD was developed where layer-by-layer modification of nc-SiH has been achieved. (Note that due to budget cuts at NREL, this project was curtailed by about one year.)