Bright trions in direct-bandgap silicon nanocrystals revealed by low-temperature single-nanocrystal spectroscopy

Abstract

Strain-engineered silicon nanocrystals (SiNCs) have recently been shown to possess direct bandgap. Here, we report the observation of a rich structure in the single-nanocrystal photoluminescence spectra of strain-engineered direct-bandgap SiNCs in the temperature range of 9-300 K. The relationship between individual types of spectra is discussed, and the numerical modeling of spectral diffusion of the experimentally acquired spectra reveals a common origin for most types. The intrinsic spectral shape is shown to be a structure that contains three peaks, approximately 150 meV apart, each of which possesses a Si phonon substructure. Narrow spectral lines, reaching f1 meV at 20 K, are detected. The observed temperature dependence of the spectral structure can be assigned to the radiative recombination of positively charged trions, in contrast to several previous reports linking a very similar shape to phonons in the surface capping layers. Our result serves as strong additional support for the direct-bandgap nature of the investigated SiNCs.

Confirmation of the Degradation of Single Junction Amorphous Silicon Modules (a-Si:H)

“…The step above was taken because soiling usually contributes to the degradation of I sc by reducing the quantity of the irradiance that reaches the front layer of the modules. However, the other parameters are not affected by soiling, but it can influence some factors which can reduce the I sc and greatly affect the performance of the modules [59,60]. One of such factors is EVA discoloration of module encapsulant.…”

Silicon Nanocrystals: From Indirect to Direct Bandgap

“…) and an organically capped Si NC (bottom, after Ref. ). (b,c) Reciprocal‐space density of states, or bandstructure, of a 1.5‐ and 2.5‐nm‐in‐dimeter hydrogen‐terminated Si NC (b) and of a 2.5‐nm oxide‐capped Si NC (c).. Real‐space localization inside the NCs is shown on the right as the red‐and‐blue spheres.…”

“…Many other important studies keep emerging, such as new types of one‐pot syntheses, or phenomena connected with light emission ranging from the tuning of SiNCs' spectra using surface groups, brightening of PL in an ensemble of SiNCs, the light‐emitting trion quasiparticles or the different modes of PL relaxation …”

Structural and luminescence properties of silicon nanocrystals in colloidal solutions for bio applications

“…In this paper, we report on structural and optical properties of Si‐ncs prepared by low‐pressure plasma synthesis and compare them with porous silicon obtained by standard electrochemical etching . Electrochemical etching is a top‐down technique producing highly porous luminescent silicon nanoclusters of hundreds nanometer size and their surface modification by methyl groups is known to lead to interesting properties such as increased luminescence quantum yield, accelerating luminescence decay , direct band gap behavior , and luminescence blinking caused by trions . Surface modification of Si‐ncs in colloidal solutions by methyl groups was carried out in plasma‐synthesized Si‐ncs, too, and the attempt to avoid agglomeration by steric stabilization of the Si‐ncs by simple organic compounds is presented (see also Ref.…”