Yellow-emitting colloidal suspensions of silicon nanocrystals: Fabrication technology, luminescence performance and application prospects

Pulverized porous silicon, fabricated by the electrochemical etching of silicon wafers, is used to prepare colloidal suspensions of silicon nanocrystals (ncSi) in various organic solvents including xylene. The porous silicon powder aggregates into large clumps, making the suspensions scatter light strongly. The suspensions are subsequently gently stirred in optical cuvettes for a period of weeks, in air and at room temperature. The temporal development of spatially resolved photoluminescence emission spectra in the cuvette with xylene+ncSi is monitored at regular intervals. The spectra show a slow evolution from the original orange color through blue to a yellow one. After approximately 5 weeks, a yellow emitting (∼560nm) transparent colloidal solution can be extracted from the cuvette, with a high and stable photoluminescence yield (∼20%).