Colloidal silicon nanocrystals (SiNCs), due to their high photoluminescence efficiency and tunable bandgap, can be used to fabricate highly efficient hybrid nanocrystal-organic light-emitting-devices (NC-OLEDs) that emit in red or near infrared spectrum. Despite reports of outstanding device performance, the underlying mechanism of this high efficiency remains unknown. Consequently, this thesis focuses on studying the electrical and optical properties of SiNCs. The electrical conductivity and mobility of electrons and holes are successfully extracted in order to explain the observed dependence of device efficiency on SiNC surface ligand coverage. Steady-state and transient photoluminescence is also examined to better understand the connection between surface ligand coverage and molecular photophysics. In addition, these measurements are used to better understand the mechanisms for non-radiative exciton decay in SiNCs. This work elucidates the relationship between SiNC properties and device performance, potentially guiding the design of future NC materials for high performance.