Blue Light Emitting Silicon Nanocrystals Prepared by Laser Ablation of Doped Si Wafers in Water

Abstract

The water-confinement of nanosecond-pulsed laser generated plasma provides great potential for preparation of ambient-stable silicon nanocrystals (Si-ncs) with quantum confinement size effect. Here, we report on blue-luminescent Si-ncs prepared by nanosecond KrF excimer laser ablation of doped-crystalline silicon target immersed in water. The Photoluminescence (PL) at low temperature show typical red-shift of the maxima assigned to the quantum confinement effect in Si-ncs. An introduction of ambient stable and less luminescent p-type doped Si-ncs into conjugated (poly(3hexylthiophene) (P3HT) polymer leads to an interaction between electronic states of the nanocrystal and the polymer. An exciton transfer from the polymer into the nanocrysatal is observed. At the same time Si-ncs blended with P3HT polymer form a bulk-heterojunction. Dissociation of the exciton and the photoconductivity generation under 1.5AM irradiation is evidenced. The ratio value of ~1.7 between photo- and dark-conductivity is achieved at ~55 wt. % concentration of Si-ncs in P3HT polymer.