Improvement of Laser Processing for Colloidal Silicon Nanocrystal Formation in a Reactive Solvent

Abstract

We report the highly improvement of colloidal Si nanocrystal (Si-nc) formation by pulsed-UV-laser irradiation of porous silicon in a HF-contained organic solvent. The Si-nc in such reactive organic solvent exhibits higher photoluminescence quantum yield (∼50–70%) than that in an ordinary organic solvent without HF (∼20%). This enhancement of the quantum yield is caused by HF-induced removal of the surface oxidation layer and subsequent hydrogen termination of the Si surface. These reaction kinetics promote an efficient hydrosilylation between the hydrogen-terminated surface and an organic solvent, resulting in oxygen-free surface terminated by alkyl groups. Furthermore, the preparation yield in the HF-contained solvent is higher and the size distribution of Si-nc becomes more homogeneous than those in the ordinary solvent. These results can be attributed to efficient pulsed-laser-induced fragmentation by the removal of the oxidation layer on the porous Si target surface.

Quantum-assisted photoelectric gain effects in perovskite solar cells

“…SiQDs were synthesized mainly using a pulsed Nd:YAG laser for 266 nm irradiation of a porous Si suspension [consisting of porous Si powder, long unsaturated alkyl ligands (i.e., 1-decence) and HF] with minor modifications according to our previous results 28,29 (see Supplementary Fig. 1 and the "Materials and methods" section).…”

“…Silicon quantum dots (SiQDs) are fascinating materials for photovoltaics [19][20][21][22][23] because of their superior properties, for example, strongly quantum-confined photoluminescence (PL) 24,25 and color-tunable emission 26,27 , as well as their nontoxic and earth-abundant nature. Recently, we successfully synthesized colloidal SiQDs through pulsed ultraviolet (UV) laser illumination of porous Si powders 28,29 . With the introduction of hydrogen fluoride (HF), the dissolution of the surface oxide is more efficient, promoting surface passivation provided by hydrogen-terminated Si surfaces.…”

Facile Formation of Stable Water‐Dispersed Luminescent Silicon Nanocrystals by Laser Processing in Liquid: Toward Fluorescent Labeling for Bio‐Imaging

“…Photoluminescence (PL) band of Si‐nc synthesized by laser irradiation process usually appears in a blue to green region, and, organically capped ones have a high stability against chemical oxidation and relatively higher PL quantum efficiency due to the smaller number of surface defects . Previously, we prepared red‐emitting Si‐nc by pulsed UV laser irradiation of PSi target in unsaturated hydrocarbon solvent . However, due to its surface ligand (i. e., hydrocarbons), the Si‐nc samples are disperse only in non‐polar solvent.…”

“…[33] Previously, we prepared red-emitting Si-nc by pulsed UV laser irradiation of PSi target in unsaturated hydrocarbon solvent. [38,39] However, due to its surface ligand (i. e., hydrocarbons), the Si-nc samples are disperse only in non-polar solvent. Thus, in the view of bioapplications of Si-nc, it is expected to form water-soluble colloidal Si-nc exhibiting PL emission in the optical window of biomaterials (i. e., a red to near infrared spectral range) by using a one-step laser process in liquid.…”

Silicon Nanocrystals with pH-Sensitive Tunable Light Emission from Violet to Blue-Green

“…Based on varied approaches of fabricating silicon NCs, including chemical vapor deposition [ 30 ], the non-thermal plasmas approach [ 20 , 31 , 32 ], electrochemical etching [ 13 , 32 , 33 ], chemical dissolution [ 16 , 34 ], annealing [ 35 , 36 , 37 ], pulsed laser ablation [ 15 , 38 , 39 ], and scanning transmission electron microscopic lithography [ 29 ], etc., various colors of silicon NC luminescence have been obtained, such as infrared [ 11 , 37 ], red [ 17 , 38 ], orange [ 13 , 40 ], yellow [ 16 ], green [ 13 , 41 ], blue [ 14 , 15 , 16 , 23 , 42 , 43 , 44 ], or multiple colors [ 21 , 45 ], etc. However, it is still a challenge to achieve controllable blue light emission of free silicon NCs without clustering, since the sizes of silicon NCs have to be much smaller than excitation Bohr radius of 4.3 nm [ 28 ] based on the quantum confinement effect [ 15 , 30 , 46 , 47 ].…”