Doping- and size-dependent photovoltaic properties of p-type Si-quantum-dot heterojunction solar cells: correlation with photoluminescence

Abstract

Boron-doped SiOx/SiO2 superlattices have been prepared on n-type Si (100) wafers by ion beam sputtering and subsequently annealed to form p-type Si quantum dots (QDs)/n-type Si-wafer heterojunction solar cells. Systematic studies on photoluminescence (PL) and photovoltaic effects show that optimum formation of Si QDs, proper doping concentration (nB), and minimization of defects are crucial factors for enhancing energy-conversion efficiency of the solar cells. Highest efficiency of 9.5% is obtained under the conditions of x=1.0 (QD size: ∼5 nm) and nB=6.3×1020 cm−3. Possible physical mechanisms are discussed to explain the correlation of the photovoltaic parameters and the QD-/defect-PL intensities. The demonstration of the photovoltaic effects in the Si-QD heterojunction solar cells is promising for the development of next-generation all-Si-QD solar cells.