Dynamics of Bound Exciton Complexes in CdS Nanobelts

Abstract

Intrinsic defects such as vacancies, interstitials, and anti-sites often introduce rich luminescent properties in II-VI semiconductor nanomaterials. A clear understanding of the dynamics of the defect-related excitons is particularly important for the design and optimization of nanoscale optoelectronic devices. In this paper, low-temperature steady-state and time-resolved photoluminescence (PL) spectroscopies have been carried out to investigate the emission of cadmium sulfide (CdS) nanobelts that originates from the radiative recombination of excitons bound to neutral donors (I(2)) and the spatially localized donor-acceptor pairs (DAP), in which the assignment is supported by first principle calculations. Our results verify that the shallow donors in CdS are contributed by sulfur vacancies while the acceptors are contributed by cadmium vacancies. At high excitation intensities, the DAP emission saturates and the PL is dominated by I(2) emission. Beyond a threshold power of approximately 5 μW, amplified spontaneous emission (ASE) of I(2) occurs. Further analysis shows that these intrinsic defects created long-lived (spin triplet) DAP trap states due to spin-polarized Cd vacancies which become saturated at intense carrier excitations.

Low‐Dimensional Perovskites: From Synthesis to Stability in Perovskite Solar Cells

“…[37,[76][77][78][79][80] Due to the flexibility and ease of employing metal films as catalysts to initiate 1D crystal growth, various groups used chemical vapor deposition (CVD) to synthesize II-VI and III-V semiconductor NWs. [81][82][83][84][85] Despite its versatility, the CVD approach is undesirable for synthesising perovskite NWs due to the low growth temperature of perovskite. Therefore, using the facile solution processable approach to prepare lead halide perovskite is the most appealing approach available to date.…”

Strain-induced spatially indirect exciton recombination in zinc-blende/wurtzite CdS heterostructures

“…Then, we performed PL measurements along the nanobelt, as indicated by the red arrow, which were excited by a 457 nm laser with a power of 50 μW at 77 K. The detailed PL peak assignment for CdS nanobelts can be found elsewhere [23]. The PL spectra show several important features: (i) The presence of strain gives rise to an additional emission peak on the low-energy side, which is indicated by the red dashed curve; (ii) with increasing strain, the position of the extra emission peak is blueshifted and Nano Res.…”

“…The experimental spectra were fitted and decomposed into individual components as shown in the series of traces. Without strain (position 1), the PL spectrum is dominated by the exciton emission with relative weak donor-acceptor pair (DAP) emission on the lowenergy side [23]. When strain is applied (position 2), an extra emission peak appears at the tail of the phonon replica of the DAP emission, and the exciton and DAP emission peaks are present as well.…”

“…Due to their excellent optical properties and visible band gap, CdS nanostructures are not only considered to be promising candidates for electrical and optoelectronic applications, such as fieldeffect transistors, waveguides, lasers, solar cells, and field emitters, but are also considered to offer adequate platforms for fundamental research [22][23][24][25][26]. The nanobelt morphology of CdS caused it to recently be identified as a novel choice of semiconductors for laser cooling applications, as it shows considerable promise for use in all solid-state optical refrigeration techniques [25,27,28].…”

Effect of boron-doping on the electroluminescence properties of CdS/Si heterostructure based on Si nanoporous pillar array

“…The G band is considered to be originated from Cd interstitial (Cd i ) to valence band (VB) [10]. The R and IR band can be attributed to the transition from sulfur vacancies (V s ) [18] to Cd vacancies (V Cd ) [19] and surface defects (SDs) [18] to sulfur interstitial ( Si ) [10]. Similar to the PL spectrum as shown in Fig.…”