Amorphous Silicon Research, Phase 1: Annual Subcontract Report, 1 August 1994 - 31 July 1995

This report describes the process made during the first year of a three-year research program to improve our understanding and capabilities for the development of multijunction hydrogenated amorphous silicon (a-Si:H) alloy cells and modules. Highlights of the work include (i) investigation of new deposition regimes/conditions such as hydrogen and He dilution, triode configuration, etc., (ii)fundamental studies to obtain the bandgap of microcrystalline p layer used in high-efficiency solar cells and band-edge discontinuity at the microcrystalline and amorphous interface, (iii) development of new techniques to analyze bulk and interface losses in solar cells, and (iv) development of high-efficiency single- and multijunction cells. The highest stable active-area cell efficiencies fordifferent cell structures were achieved using hydrogen dilution during deposition and are as follows: (1) a:Si:H single-junction-8.8%, (2) a-Si:H/a-Si:H same gap double-junction-10.1%, (3) a-Si:H/a-SiGe:H dual gap double-junction-11.2%, (4) a-Si:H/a-SiGe:H/a- SiGe:H triple gap triple-junction-11.1%. All these results are the highest reported in the literature.