Codoping n- and p-Type Impurities in Colloidal Silicon Nanocrystals: Controlling Luminescence Energy from below Bulk Band Gap to Visible Range

Abstract

We present a novel synthesis of ligand-free colloidal silicon nanocrystals (Si-NCs) that exhibits efficient photoluminescence (PL) in a wide energy range (0.85–1.8 eV) overcoming the bulk Si band gap limitation (1.12 eV). The key technology to achieve the wide-range controllable PL is the formation of donor and acceptor states in the band gap of Si-NCs by simultaneous doping of n- and p-type impurities. The colloidal Si-NCs are very stable in an ordinary laboratory atmosphere for more than a year. Furthermore, the PL spectra are very stable and are not at all affected even when the colloids are drop-cast on a substrate and dried in air. The engineering of the all-inorganic colloidal Si-NC and its optical data reported here are important steps for Si-based optoelectronic and biological applications.

Energy Transfer in Silicon Nanocrystal Solids Made from All-Inorganic Colloidal Silicon Nanocrystals

“…It decreases gradually to smaller size and rapidly to larger size. 49 In Figure 2, C1050 exhibits PL around 1.7 eV, while C1200 exhibits it around 1.2 eV. The size dependence of the PL energy is consistent with the previous work.…”

“…The PL properties of B and P codoped Si-NCs have been studied in detail previously. 49 The PL energy depends strongly on the size and increases with decreasing the size. The PL energy of codoped Si-NCs is always 200 to 300 meV smaller than that of undoped Si-NCs with identical sizes, and the lifetime is shorter than that of undoped ones.…”

Luminescent silicon nanocrystals produced by near-infrared nanosecond pulsed laser ablation in water

“…In particular, it has been evidenced that in small Si-NCs (size ∼3 nm) surface oxidation produces localized states at Si O Si bridge or Si O double bonds which favor the enhancement of the red emission [21,22]. Also the doping is expected to influence the PL properties; a recent work has indeed pointed out that n-and p-type codoping introduces donor and acceptor states that lower the PL energy transition [23]. Regardless its origin, we note that the peak position at 1.95 eV agrees with the QC effect.…”

Size-Selective Separation Techniques for Nanoparticles in Liquid

“…et al, 2006;Sugimoto H. et al, 2013). When particle size is controlled, NPs can be applied in sensors (Anker J.N.…”