Photoluminescence Properties of Mechanochemically Synthesized Silicon Quantum Dots

Abstract

Nanocrystalline silicon has drawn immense research interest due to its unique optoelectronic properties and attractive potential applications. Numerous models were suggested to explain the intense visible photoluminescence from silicon nanostructures. However, combined effect of quantum confinement and defect related emissions are most accepted among the scientific community as the source of efficient broad photoluminescence spectrum of silicon nanocrystal/ silicon oxide systems in the visible region. newlineInvestigation on the photoluminescence behavior of silicon nanostructures helps to understand the usability of such materials in nano-photonic devices utilizing quantum physics. Due to the bandgap widening owing to quantum confinement and large surface to volume ratio, nano-silicon has enormous potential not only in photonics but also in photovoltaics, memory devices and sensors. In this work, investigation on the optoelectronic properties especially photoluminescence behavior of silicon quantum dot/silicon oxide core/shell nanostructures has been performed to understand their prospect in futuristic 3rd generation photovoltaics like hot carrier solar cell. newlineColloidal suspension of luminescent freestanding silicon/silicon oxide core/shell nanostructures was synthesized utilizing the mechanical milling process followed by several chemical and thermal treatments. Nano dimensional silicon/silicon oxide core/shell quantum dot like structures were achieved from the silicon wafer as the end product. However, it was found that synthesized silicon/silicon oxide core/shell nanostructures have vast core size distribution. Investigation of quantum confinement induced properties (especially photoluminescence behaviour) of synthesized nano-silicon systems is possible only when there is a narrow size distribution of silicon cores in a quantum size range i.e. below the free exciton Bohr radius of bulk crystalline silicon. Therefore, a step by step size segregation process which consists of repetitive sonication and centrifugation s