In CO2 electroreduction, the critical bottleneck lies in the CO2 activation which requires high overpotentials. CO2 activation is related to both the electronic structures of catalysts and those of...

Harmonizing the Electronic Structures of the Adsorbate and Catalysts for Efficient CO2 Reduction.

Nanodimensional metal sulfides are a developing class of low-cost materials with potential applications in areas as wide-ranging as energy storage, electrocatalysis, and imaging. An attractive synthetic strategy, which allows careful control over stoichiometry, is the single source precursor (SSP) approach in which well-defined molecular species containing preformed metal-sulfur bonds are heated to decomposition, either in the vapor or solution phase, resulting in facile loss of organics and formation of nanodimensional metal sulfides. By careful control of the precursor, the decomposition environment and addition of surfactants, this approach affords a range of nanocrystalline materials from a library of precursors. Dithiocarbamates (DTCs) are monoanionic chelating ligands that have been known for over a century and find applications in agriculture, medicine, and materials science. They are easily prepared from nontoxic secondary and primary amines and form stable complexes with all elements. Since pioneering work in the late 1980s, the use of DTC complexes as SSPs to a wide range of binary, ternary, and multinary sulfides has been extensively documented. This review maps these developments, from the formation of thin films, often comprised of embedded nanocrystals, to quantum dots coated with organic ligands or shelled by other metal sulfides that show high photoluminescence quantum yields, and a range of other nanomaterials in which both the phase and morphology of the nanocrystals can be engineered, allowing fine-tuning of technologically important physical properties, thus opening up a myriad of potential applications.

Dithiocarbamate Complexes as Single Source Precursors to Nanoscale Binary, Ternary and Quaternary Metal Sulfides.

Aqueous solution-processed methods offer several advantages such as simplicity, low-cost, environmental friendliness, and easy scale up. Herein, we present an ultrafast and convenient aqueous route to prepare off-stoichiometric Cu–In–S quantum dots (QDs) including CuInS2, a mixture of In2S3 and CuInS2 (In2S3/CIS), and Mn-doped In2S3/CIS (Mn:Cu–In–S), obtained by simply adjusting the feed ratio of Cu and In precursors in an identical procedure. Such off-stoichiometric QDs were then exploited as photon-harvesters in quantum dot-sensitized solar cells (QDSSCs), which showed superior photovoltaic performance that is dependent on the [Cu]/[In] feed ratio. The QDSSCs sensitized with In2S3/CIS QDs exhibited a cell efficiency as high as 7.53%, a more promising performance than that of the device sensitized with CuInS2 QDs (1.0%). Such an improvement of the photovoltaic performance can be attributed to the favorable energy level alignment of the adjoining materials (the TiO2 semiconductor and In2S3/CIS QDs). Upon incorporation of Mn2+ into In2S3/CIS under identical conditions, the power conversion efficiency of the Mn:Cu–In–S-based QDSSC reached 8.0% due to a synergistic effect between the In2S3 QDs and Mn2+ dopant. Analyses of the Bader charge and projected density of states based on density functional theory (DFT) calculations revealed that the coexistence of In2S3 and Mn2+ enhances the electronic coupling at the TiO2/QD interface, leading to a larger number of photoinduced electrons being injected into TiO2. Electrochemical impedance spectroscopy and intensity-modulated photocurrent/photovoltage spectroscopy measurements confirmed the slower charge recombination and prolonged electron lifetimes that result in the excellent efficiency of the QDSSC device sensitized with Mn:Cu–In–S QDs.

Aqueous solution-processed off-stoichiometric Cu–In–S QDs and their application in quantum dot-sensitized solar cells

Inorganic two-dimensional semiconductor nanostructures intrigue the scientific community because of their tunable and sparse electronic states and their high conductivity. The current work deals with colloidal nanoplatelets (NPLs) based on In2S3 compound, focusing on the growth mechanism that leads to the formation of two different phases, trigonal γ-In2S3 and defect spinel β-In2S3, both stabilized at room temperature and characterized by ordered metal voids. In particular, we substantiate the experimental factors (e.g., temperature, reaction duration, and surface ligands) that control the growth progress. The results indicated the formation of hexagonal NPLs of the γ-phase at an elevated temperature and dodecagon NPLs of the γ-phase at a lower temperature. A long-reaction duration time transformed the hexagons/dodecagons into truncated triangular shapes. Furthermore, the analysis of thermodynamic and kinetic factors indicated a phase transformation from the γ-phase to the β-phase. All phases were produce...

Unraveling the Growth Mechanism Forming Stable γ-In2S3 and β-In2S3 Colloidal Nanoplatelets

As one of the most promising third-generation photovoltaics devices, quantum dot-sensitized solar cells (QDSCs) have attracted increasing attention due to their easy fabrication, low cost, potential high efficiency, etc. Thus, substantial efforts have been taken to boost their photoelectrical conversion efficiencies (PCEs) and device stability consistently by precisely optimizing the structure of materials and device architecture. Throughout the development of QDSCs, it is noteworthy to mention that metal chalcogenide-based semiconductors have been key materials in capturing sunlight as sensitizers, catalytic electrolyte reduction as counter electrodes (CEs), and interface charge transport as interface modification layers. Herein, we systematically review the recent progress on metal chalcogenide-based QDSCs in practical applications from three main functional points, specifically, QD sensitizers, counter electrodes (CEs), and interface modification layers. Besides, we have outlined the fundamental structure, operation principle, and brief history of these sensitized solar cells. Finally, the state of existing challenges and future prospects for QDSCs employing various metal chalcogenides are also discussed.

Recent progress in quantum dot-sensitized solar cells employing metal chalcogenides

Indium sulphide (In2S3) quantum dots (QDs) of average size 6 ± 2 nm and hexagonal nanoplatelets of average size 37 ± 4 nm have been synthesized from indium myristate and indium diethyl dithiocarbamate precursors respectively. The absorbance and emission band was tuned with variation of nanocrytal size from very small in the strong confinement regime to very large in the weak confinement regime. The blue emission and its shifting with size has been explained with the donor-acceptor recombination process. The 3d element doping (Mn(2+) and Cu(2+)) is found to be effective for formation of new emission bands at higher wavelengths. The characteristic peaks of Mn(2+) and Cu(2+) and the modification of In(3+) peaks in the x-ray photoelectric spectrum (XPS) confirm the incorporation of Mn(2+) and Cu(2+) into the In2S3 matrix. The simulation of the electron paramagnetic resonance signal indicates the coexistence of isotropic and axial symmetry for In and S vacancies. Moreover, the majority of Mn(2+) ions and sulphur vacancies (VS ) reside on the surface of nanocrystals. The quantum confinement effect leads to an enhancement of band gap up to 3.65 eV in QDs. The formation of Mn 3d levels between conduction band edge and shallow donor states is evidenced from a systematic variation of emission spectra with the excitation wavelength. In2S3 QDs have been established as efficient sensitizers to Mn and Cu emission centers. Fast and slow components of photoluminescence (PL) decay dynamics in Mn and Cu doped QDs are interpreted in terms of surface and bulk recombination processes. Fast and stable photodetctors with high photocurrent gain are fabricated with Mn and Cu doped QDs and are found to be faster than pure In2S3. The fastest response time in Cu doped QDs is an indication of the most suitable system for photodetector devices.

https://iopscience.iop.org/article/10.1088/0957-4484/27/15/155708/pdf

Excitation dependent multicolor emission and photoconductivity of Mn, Cu doped In2S3 monodisperse quantum dots.

/pdf/cumitherm-a-state-of-the-art-zero-expansion-ceramics-and-its-jm3x3ozxzh.pdf

Arijit Chatterjee

Papers

Excitation dependent multicolor emission and photoconductivity of Mn, Cu doped In2S3 monodisperse quantum dots.

CUMITHERM®– A State-of-the-art Zero Expansion Ceramics and its Applications