Advanced deposition phase diagrams for guiding Si:H-based multijunction solar cells

Abstract Phase diagrams have been established to describe very high frequency (vhf) plasma-enhanced chemical vapor deposition (PECVD) processes for intrinsic hydrogenated silicon (Si:H) and silicon-germanium alloy (Si_1-xGe_x:H) thin films using crystalline Si substrates that have been over-deposited with n-type amorphous Si:H (a-Si:H). The Si:H and Si_1-xGe_x:H processes are applied for the top and middle i-layers of triple-junction a-Si:H-based n-i-p solar cells fabricated at University of Toledo. Identical n/i cell structures were co-deposited on textured Ag/ZnO back-reflectors in order to correlate the phase diagram and the performance of single-junction solar cells, the latter completed through over-deposition of the p-layer and top contact. This study has reaffirmed that the highest efficiencies for a-Si:H and a-Si_1-xGe_x:H solar cells are obtained when the i-layers are prepared under maximal H₂ dilution conditions.