White light luminescence from nano-ZnS doped porous silicon

Abstract

Nano-ZnS was deposited into porous silicon. By varying the concentration of Zn2+ ion solution during nano-ZnS formation, the amount of nano-ZnS in the porous silicon host can be controlled. The doped porous silicon exhibited a gradual shift in its photoluminescence peak from red to blue as a function of the nano-ZnS coverage. At an optimum doping, white light photoluminescence was obtained. A study in the luminescence lifetime has shown that the radiative recombination at the blue end of the visible spectrum was due to nano-ZnS, whereas luminescence emission at the red end of the visible spectrum came from porous silicon. The latter luminescence was due to the tunnelling of excited electrons from nano-ZnS into porous silicon. Time-resolved photoluminescence has also shown that radiative recombination was effectively dominated by the nano-ZnS. The photoluminescence excitation results revealed the presence of two excitation levels: one belonging to nano-ZnS at the near-ultraviolet region, and another at about 520 nm from the surface states of porous silicon. The doping of nano-ZnS into porous silicon demonstrates that luminescence colour tuning is possible when an appropriate functional material is introduced into porous silicon.

Bright White‐Light Emission from Semiconductor Nanocrystals: by Chance and by Design

“…There are a few articles that report the synthesis of semiconductor NCs with white-light emission. [5][6][7][8][9] These systems are based upon ZnS:Pb, [5] ZnS incorporated in porous Silicon, [6] ZnSe, [7] Mn-doped ZnS, [8] and the most recently reported "magic-sized" CdSe NCs. [9] However, all these systems rely on the surface-state emission from the NCs, which we call here "emission by chance".…”

Investigation of the photoluminescence properties of thermochemically synthesized CdS nanocrystals

“…17 Two hydroxyl group of TG are negative at the basic media that prevent their undesirable growth. In the basic media terminal groups of TGA are partially charged and the carbonyl oxygen of TGA may coordinate with Cd cites of monomers or cluster to as secondary coordination, and also carbon chain of TGA is shorter than that of TG, therefore in the same concentration, TGA can capped non radiative paths of nanocrystals better than TG.…”

“…15 There are a few articles that reported synthesis of white-color light emitting nanoprticles. [16][17][18][19][20][21][22] CdS nanocrystals were synthesized with a new thermochemical method using thioglycerol (TG) as capping agent in our group, 23 here also we have synthesized CdS nanocrystals with this method but thioglycolic acid (TGA) has been used instead of TG as capping agent molecule. X-ray diffraction (XRD) and TEM analyses demonstrated hexagonal phase CdS nanocrystals with an average size around 2 nm and a good size distribution.…”

Synthesis of fluorescent core-shell nanomaterials and strategies to generate white light

“…several reports describing the synthesis of semiconductor nanocrystals (NCs) with white light emission such as CdSe NCs, alloyed Zn x Cd 1Àx Se QDs, ZnS:Pb, and ZnS incorporated into porous silicon, Mn, Cu co-doped ZnSe, and ZnS:Mn QDs. [16][17][18][19][20][21] It is expected that a high quality white light emission from a mixture of differently doped QDs can be achieved. The problems associated with a simple mixing are reabsorption of the emitted photon by other QDs, excitation of mixture of QDs at different wavelengths, and out of phase emission of different QDs.…”