Direct observation of significant hot carrier cooling suppression in a two-dimensional silicon phononic crystal

Abstract

Finding hot carrier cooling suppression in new material structures is fundamentally important for developing promising technological applications. These phenomenona have not been reported for crystalline silicon phononic crystals. Herein, we experimentally design two-dimensional (2D) silicon samples consisting of airy hole arrays in a crystalline silicon matrix. For reference, the determined hot carrier cooling times were 0.45 ps and 0.37 ps, respectively, at probe wavelengths of 1080 nm and 1100 nm. Surprisingly, when the 2D structured silicon possessed the properties of a phononic crystal, significant suppression of hot carrier cooling was observed. In these cases, the observed hot carrier cooling times were as long as 15.9 ps and 10.7 ps at probe wavelengths of 1080 nm and 1100 nm, respectively, indicating prolongation by orders of magnitude. This remarkable enhancement was also observed with other probe wavelengths. The present work presents experimental evidence for hot carrier cooling suppression in 2D silicon phononic crystals and opens opportunities for promising applications.

Stimulating Phonon Bottleneck Effect in Organic Semiconductors by Charge-Transfer-Mediated J-Aggregation

“…The hot phonon bottleneck effect has been extensively studied in inorganic semiconductors, such as Si, GaN, CdSe, and perovskite . The effect is typically achieved at a high carrier density (>10 18 cm –3 ) where carrier–phonon interactions are screened and the Auger heating effect is significant. , To understand the effect in the CT-mediated J-aggregates, a pump power-dependent experiment from 6 to 1400 μW was performed.…”

“…Under S 1 + state excitation, efficient coupling between the two states of S 1 + and S 1 − will take place, resulting in an efficient delocalization of electrons in the excited state and the observation of an extremely slow carrier cooling, typically 2−3 orders slower than the S 1 − state pumping. The hot phonon bottleneck effect has been extensively studied in inorganic semiconductors, such as Si, 29 GaN, 30 CdSe, 1 and perovskite. 31 The effect is typically achieved at a high carrier density (>10 18 cm −3 ) where carrier−phonon interactions are screened and the Auger heating effect is significant.…”

Unraveling Its Intrinsic Role of CH3NH3Cl Doping for Efficient Enhancement of Perovskite Solar Cells from Fine Insight by Ultrafast Charge‐Transfer Dynamics

“…The fs-TA measurements were performed employing a regenerative amplified Ti:sapphire laser system (coherent; 800 nm, 85 fs, 7 mJ pulse À1 , and 1 kHz repetition rate) as the laser source and a Helios spectrometer (Ultrafast Systems LLC), as described previously. [31,32] As briefly described, the 800 nm output pulse from the regenerative amplifier was split into two parts using a 50% beam splitter. The transmitted portion was used to pump a TOPAS optical parametric amplifier (OPA), which generated a wavelength-tunable laser pulse from 250 nm to 2.5 μm as a pump beam.…”

Experimentally revealed and theoretically certified synergistic electronic interaction of V-doped CoS for facilitating the oxygen evolution reaction

“…25 Density functional theory (DFT) calculations show that appropriate simultaneous doping of Co, S and V can heighten the density of states (DOS) at the Fermi level, which can generate more charge density and reduce the intermediate adsorption energy. 26 This work not only details highly efficient and robust integrated catalysts, but also a regulable oxygen insertion technique and design concept, which makes it of wide appeal to basic research and practical applications in electrocatalysis. 27…”