title: Shrinking and growing: grain boundary density reduction for efficient polysilicon thin-film solar cells.
abstract: Polycrystalline Si (poly-Si) thin-film, due to its low Si consumption, low substrate cost, and good stability, is an attractive candidate for cost-effective solar cells, but the as-deposited poly-Si typically has a columnar structure with grain boundaries in between, severely limiting the efficiency of the poly-Si. Here, we report a micropillar poly-Si solar cell that utilizes the columnar structure of the as-deposited poly-Si grains. We first formed submicrometer diameter poly-Si pillars, smaller than the initial grain sizes, and used these pillars as the seeds for the subsequent epitaxial growth of Si, which effectively reduces grain boundary density in the final poly-Si crystal. In addition, the vertically aligned micropillar arrays form radial p-n junctions that further mitigate the grain boundary recombination losses by improving the light absorption and charge-carrier collection efficiencies. Consequently, the maximum efficiency of micropillar poly-Si thin-film solar cells is 6.4%, that is, ∼1.5 times higher than that of the planar cells.
authors.affiliation: Department of Mechanical Engineering, Hanyang University, Seoul 133-791, Korea.
authors.forename: Dong Rip
authors.initials: DR
authors.lastname: Kim
authors.forename: Chi Hwan
authors.initials: CH
authors.lastname: Lee
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Weisse
authors.forename: In Sun
authors.initials: IS
authors.lastname: Cho
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Zheng
mesh_terms: D011211:Electric Power Supplies; D004867:Equipment Design; D049329:Nanostructures / Q000737:chemistry; D012825:Silicon / Q000737:chemistry*; D012993:Solar Energy
chemical_list: D012825:Silicon