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

Boron-doped SiO x / SiO 2 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 ( n B ) , 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 n B = 6.3 × 10 20 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.