[17p-A403-1~17] 16.3 Bulk, thin-film and other silicon-based solar cells

▲ [17p-A403-11] Clarifying the effects of nanostructured porosity of silicon on the band gap and band alignment: a computational study

Panus Sundarapura¹, Manabu Ihara¹, 〇Sergei Manzhos¹ (1.Tokyo Tech)

Keywords:porous silicon, tandem solar cell, density functional tight binding

Porous silicon (pSi) has been studied for its applications in solar cells, in particular in silicon-silicon tandem solar cells. It is commonly believed that porosity leads to an expansion of the band gap due to nano-confinement. Direct confirmation of this proposition has been elusive, as experimental band edge quantification is subject to uncertainties and effects of impurities, while electronic structure calculations at relevant length scales are still outstanding. Passivation of pSi presents another factor affecting band structure. We present combined molecular dynamics – density functional tight binding study of the effects of porosity of silicon on its band structure at length scales relevant to real pSi. We consider multiple nanoscale geometries (pores, pillars, craters) with key geometric features and sizes of real porous Si. We show that the band gap expansion does not trend with the pore size but with the size of the Si framework. We show that a significant band expansion would require engineering sizes of features of silicon (as opposed to pore sizes) as small as 1 nm, while the nanosizing of pores does not induce gap expansion.