Design And Fabrication Of Advanced Micro/Nano Light-trapping Structures For Solar Cells Applications

Silicon based nanostructured solar cells show great potential for the next generation photovoltaics due to their abilities to achieve ideal light-trapping.The enhancement in optical absorption induced by the advanced light trapping structures is a key issue to fabricate high efficiency solar cells with low costs.However,the nano-featured morphology which brings about the optical benefits will also introduce new recombination channels.The severe deterioration in the electrical performance induced by the recombination may even outweighs the gain in optics in most attempts.In this work,we developed a one-step metal assisted chemical etching(MACE)process,in which the nucleation of Ag catalyses occurring along with etching.This is different from the ordinary MACE,where the nucleation of Ag and the initiation of etching(by Ag catalyses)are divided into two sequential steps.Due to the simultaneous occurrence of nucleation of Ag and Si etching,the Ag is constantly deposited on the top side wall of the Si to continue the etching and finally forms the top opening structures.At the same time,we fabricated low aspect ratio hierarchical structures on silicon(Si)surface with atomically smooth surfaces by the control of the composition in one step MACE etching solution.In comparison with conventional black Si,this hierarchical structure finally showed a great improvement in optical performance and could realize alleviative deterioration in electrical properties.The principal results of this thesis are listed as follows:1 We fabricate hierarchical V-nanopore structures by MACE that achieve an conformal coverage on the top about 50 nm PEDOT:PSS and exhibit both outstanding electric performances and excellent antireflection in broadband wavelength ranges.These enhancements contribute to a high power conversion efficiency(PCE)of 11.31%,which is much larger than the conventional Si NWs structures of 11%.2 With the precise control of the etching solution composition,low aspect ratio bowl-like nanostructures with smooth surfaces could be directly achieved by improved one-step MACE without any post-treatment by alkali solution.The doublet surface texture of implementing nanobowl structure upon the industrialized acidic textured-surface showed great improvements in both optical and electrical properties for realizing 18.23%-efficiency mc-Si solar cells(156 mm × 156 mm),sufficiently higher than 17.7% of the solely acidic textured cells in the same batch.