Advance Hydrogen Passivation Process Apply on SiGe/Si Tandem Device
Due to the formation of islanding and misfit dislocations at the interface,lattice mismatch is an important concern for monolithic III-/Si tandem solar cells.The application of Si1-XGeX buffer layers has shown potential in reducing the lattice-mismatch between Si and III-V materials.Significant recombination losses could be brought on by dislocations and dangling bonds among the Si1-XGeX buffer layers,though.In order to decrease the buffer layer and base region defects and hence enhance the performance of Si1-XGeX cells grown on Si with Si1-XGeX graded buffer layers in between,we employ an improved hydrogenation technique in this work.Using PECVD,SiNx has been applied to SiGe/Si cells with four distinct Ge concentrations(78%,82%,85%and 88%),serving as both an anti-reflection coating and a source of hydrogen.Voc and efficiency of SiGe cells,with 78%,82%and 85%Ge concentration,after 30 seconds of cumulative laser irradiation,were enhanced by 2%～4%REL(6～12 mV)and 5%～17%REL,respectively.These findings show that hydrogenation passivation works well on Si1-XGeX buffer layers and SiGe base defects.They also point to potential new uses for the advanced hydrogenation method on other tandem devices.
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