Wurtzite CuInS2 Research Articles

Colloidal synthesis of wurtzite CuInS2 nanocrystals and their photovoltaic application

Ternary wurtzite CuInS2 nanocrystals were successfully synthesized and characterized by X-ray powder diffraction, energy dispersive X-ray spectrometry, transmission electron microscopy and UV–vis spectrometry. In this paper, the solar cell is fabricated by as-synthesized wurtzite CuInS2 nanocrystals as absorber layer. The J–V property of the CdS/CuInS2 solar cell shows that the open-circuit voltage is 0.409V and the short-circuit current is 0.5mA/cm2 under 1.5G illumination. All of J–V result displays that as-synthesized CuInS2 nanocrystals can be directly applied in thin film solar cells.

The synthesis of hollow CuInS2 microspheres with hierarchical structures

Hollow CuInS2 microspheres with hierarchical structures were synthesized via solution-based method. The detailed HRTEM and XRD results demonstrated the presence of zincblende CuInS2 microspheres trunks and wurtzite nanobelts attached onto the microspheres. As it was found, oxygen had decisive effect on the formation of CuInS2 microspheres. Detailed investigation indicated the growth of hierarchical structured CuInS2 microspheres simultaneously underwent two different mechanisms, phase transformation for zincblende CuInS2 microspheres and catalytic growth for wurtzite CuInS2 nanobelts.

Electronic and Optical Structure of Wurtzite CuInS2

We present a theoretical study of the electronic structure of the wurtzite CuInS2 material. To address reliably some material properties of this new phase we use hybrid density functional theory. Among possible wurtzite polymorphs, we have determined the most stable phase on the basis of total energy minimization. The minimum energy structure exhibits a semiconducting ground state with a band gap of ∼1.3 eV in excellent agreement with experimental data. We use time-dependent density functional theory to compare the optical response of the chalcopyrite and wurtzite phases and to identify the nature of the optically active transitions in the vicinity of the absorption edge. Our analysis indicates that the wurtzite CuInS2 structure is a suitable material for photovoltaic applications.

One-pot controllable synthesis of wurtzite CuInS2 nanoplates

Abstract Wurtzite CuInS 2 nanoplates have been synthesized using a simple one-pot colloidal chemical method, which is a direct heating process without any injection and pre-synthesis of any metal precursors. The transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed to characterize their morphology, crystalline phase, and composition, respectively. By changing the reaction conditions, such as reaction time, reaction temperatures and the Cu:In precursors ratio, the nanoplate thickness and composition can be tailored effectively. By monitoring the growth process of the as-obtained CuInS 2 nanoplates, it found that the monoclinic Cu 1.94 S nanocrystals were firstly formed and gradually transformed to CuInS 2 nanoplates with the increasing reaction time.

Selective synthesis of cubic and hexagonal phase of CuInS2nanocrystals by microwave irradiation

Metastable cubic zincblende and hexagonal wurtzite CuInS2 nanocrystals were successfully synthesized by a facile microwave radiation method. The morphology, structure and phase composition of the as-prepared products were examined, and the results demonstrated that high-purity and uniform CuInS2 nanocrystals were obtained. Further investigation revealed a structural evolution process from cubic zincblende to hexagonal wurtzite with increasing volume ratio of ethylenediamine and ethanol from 1 : 30 to 1 : 1 at 160 °C. In addition, the optical absorption properties of samples were also studied. It was found that the as-synthesized cubic and hexagonal CuInS2 nanocrystals had band gaps of 1.503 and 1.470 eV, respectively. Thanks to the superior optical absorption properties for visible light, CuInS2 nanocrystals may have potential applications in various nanostructured optoelectronic devices. The possible formation mechanism of the product, namely “phase transformation”, was systematically studied.

Influence of crystal phase for CuInS2 on device performance of polymer–CuInS2/oxide nanoarrays solar cells

The paper demonstrates the influence of crystal phase for CuInS2 on device performance of MEH-PPV-CuInS2/oxide nanoarrays hybrid polymer-based solar cells. CuInS2 quantum dots with wurtzite and chalcopyrite crystallographic phases are incorporated into pristine polymer layer as light-harvesting hybrids, while ZnO nanoarrays (ZnO-NA) and TiO2 nanoarrays (TiO2-NA) are used as electron acceptor. Results show that devices with wurtzite CuInS2 quantum dots (WCIS-QDs) exhibited higher photovoltaic performance in MEH-PPV-CuInS2/ZnO-NA solar cells, while devices with chalcopyrite CuInS2 quantum dots (CCIS-QDs) exhibited higher performance in MEH-PPV-CuInS2/TiO2-NA solar cells. It is concluded that the devices based on metal oxide and CuInS2 that belong to the same crystal system contribute to the increased device performance, which possibly results from the more effective energy transfer and transport between metal oxide and CuInS2 with the same crystal system.

Mild solution-based method for synthesizing wurtzite CuInS2 nanoplates at low temperature

Wurtzite copper indium disulfide (CuInS2) nanoplates were synthesized via a low-cost, facile solution-based method. The reaction was carried out at 140°C for an hour under nitrogen atmosphere by using the solvent of monoethanolamine (MEA). The experimental results revealed that the products had good crystallinity, monomorphology and stoichiometric composition. The solvent material, reaction time and temperature played important roles in the formation of the wurtzite CuInS2 nanoplates. The possible growth mechanism was also proposed and discussed. And the wide stoichiometry of the wurtzite-CuInS2 implies that this work may offer a new strategic approach for the synthesis of I–III–VI2 ternary semiconductor nanocrystals as new solar energy materials.

Synthesis of metastable wurtzite CuInS2 nanocrystals and films from aqueous solution

For the first time, metastable wurtzite CuInS2 nanocrystals and films were successfully synthesized from aqueous solution under atmospheric conditions. The CuInS2 nanocrystals were prepared by stirring and reflux of a metal salt and sodium sulfide in aqueous solution containing thioglycolic acid as a stabilizer. The good absorption in the visible light region may find interesting application in solar cells. The I–V curve indicated that the wurtzite CuInS2 NCs favored the generation of photoinduced carrier and electronic transmission. The proposed synthesis strategy may be used as a general process for the synthesis of hydrophilic chalcogenide semiconductor NCs and is scalable for commercial production with minimal environmental impact.

Oleic acid assisted formation mechanism of CuInS2 nanocrystals with tunable structures

CuInS2 nanocrystals with different phase structures were synthesized by a facile heat-up method through simply adjusting the OA dosage. This is because a high OA dosage could facilitate the formation and crystallization of the CuIn(SR)x intermediate, giving a metastable wurtzite CuInS2 structure, while low OA dosage would lead to low crystallinity of the intermediate, producing a stable zinc-blende phase.

Synthesis and formation mechanism of CuInS2 nanocrystals with a tunable phase

Monodisperse chalcopyrite and wurtzite CuInS2 nanocrystals are produced and their crystal phases are controlled by varying the In precursors.

A generalized strategy for controlled synthesis of ternary metal sulfide nanocrystals

Ternary metal sulfide nanocrystals (TMS NCs) have drawn intense attention for their wide applications in photovoltaics and nanophotonics, etc. However, a facile and general method for controlled synthesis of TMS NCs with uniform size and pure crystal phase is yet to be realized. Here we report a simple and versatile one-pot method for preparing high quality TMS NCs with controlled morphologies, sizes, crystalline structures and compositions, including orthorhombic Cu3BiS3 nanosheets and nanoparticles, orthorhombic Cu4Bi4S9 nanowires and nanoribbons, wurtzite CuInS2 nanopencils, cubic AgBiS2 nanocubes, orthorhombic Ag8SnS6 nanoparticles, and orthorhombic Cu3SnS4 nanorods, based on the co-thermal decomposition of metal-diethyl dithiocarbamate (metal-DDTC) precursors. We expect that this methodology will be broadly applicable for synthesizing new metal sulfide NCs and play an important role in exploring their new properties for various applications.

Fabrication of hollow-sphere films of wurtzite CuInS2 on copper substrate

As important semiconductors, I–III–VI2 compounds have attracted wide attention, among which the wurtzite structured CuInS2 has been the research focus due to its metastable phase. In this paper, the wurtzite CuInS2 hollow-sphere films have been successfully prepared on copper substrate in a self-designed solvothermal detached system. The films of Cu(OH)2 one-dimensional nanostructure arrays and thioacetamide were used as the precursors and triethylene glycol was used as the solvent. Experiments showed that the amount of indium trichloride played a determinative role in the final morphology of the products. Meanwhile, the one-dimensional nanostructure arrays and the detached solvothermal system have great influences on the crystal shape as well. Based on the experimental results, a possible formation mechanism for the CuInS2 hollow spheres was also proposed. The UV–Vis absorption spectrum showed a broad absorption over the entire visible light and extending into the near-infrared region and presented the band gap of 1.53 eV for the as-prepared wurtzite CuInS2, which indicates the potential applications in solar cells.

ChemInform Abstract: Spinel Indium Sulfide Precursor for the Phase‐Selective Synthesis of Cu—In—S Nanocrystals with Zinc‐Blende, Wurtzite, and Spinel Structures.

AbstractZinc‐blende CuInS2, wurtzite CuInS2, and spinel CuIn5S8 nanocrystals are solvothermally synthesized from mixtures of Cu(S2C‐NEt2)2 or Cu(OAc)2, In3‐xSx, liquid paraffin, and various solvents such as 1‐dodecanethiol, oleylamine, oleic acid, or a mixture of oleylamine and oleic acid (autoclave, 180 °C, 12 h).

Spinel Indium Sulfide Precursor for the Phase-Selective Synthesis of Cu–In–S Nanocrystals with Zinc-Blende, Wurtzite, and Spinel Structures

Group I–III–VI ternary chalcogenides have attracted extensive attention as important functional semiconductors. Among them, Cu–In–S compounds have seen strong research interest due to their potential applications in high-efficiency solar cells. However, the controllable synthesis of Cu–In–S nanostructures with different phases is always difficult. In this research, zinc-blende CuInS2, wurtzite CuInS2, and spinel CuIn5S8 could be selectively synthesized using spinel In3–xS4 as the precursor by a simple solvothermal method. X-ray powder diffraction was used to determine the phase and crystal structure, and transmission electron microscopy was employed to characterize the morphologies of the as-prepared samples. Experiments showed that the acidity–basicity of the reaction system and the coordination and reducibility of the capping ligands were crucial to the final phases of the products. The UV–vis–NIR spectra of the three phases all exhibited a broad-band absorption over the entire visible light and extendi...

Behaviors of Fe, Zn, and Ga Substitution in CuInS2 Nanoparticles Probed with Anomalous X-ray Diffraction

We synthesized CuInS2 nanoparticles containing up to 20% Fe, Zn, and Ga to study alloying in photovoltaic absorber materials with anomalous X-ray diffraction. The colloidal synthesis allowed for detailed analysis of complex quaternary compounds. Anomalous X-ray diffraction (AXRD) was used to clarify the elemental distribution between phases. Additionally, optical spectroscopy and X-ray diffraction were used to probe the band gap and crystal phase, respectively. Substitution of Zn into wurtzite CuInS2 produced a controllable increase in the optical band gap, whereas Ga did not substitute into wurtzite CuInS2, producing no band gap change. Secondary phase precipitation of a chalcopyrite phase was observed with Fe substitution, along with a decrease of the optical band gap. This work demonstrates progress in compositional and structural analysis of quaternary chalcogenide materials using AXRD.

Wurtzite CuInS2: solution based one pot direct synthesis and its doping studies with non-magnetic Ga3+ and magnetic Fe3+ ions

Reactions of air stable copper-thiourea precursors [Cu(tu)3]Cl and [Cu2(tu)6]SO4·H2O with indium(III) acetate (In(OAc)3·xH2O) and indium(III) sulfate (In2(SO4)3·xH2O) under refluxing in ethyleneglycol for 1–3.5 h yielded metastable, wurtzite (WZ) and zincblende (ZB) forms of CuInS2 (CIS). While the yields of CIS from the reactions using In2(SO4)3 were quite high, reactions involving In(OAc)3 were sluggish producing low yields. A flower like morphology has been observed in the FE-SEM image of the WZ-CIS with EDX analysis yielding Cu : In : S ratio as 1.05 : 0.95 : 2.00. The SAED pattern of WZ-CIS recorded from the HR-TEM images could very well be indexed in hexagonal symmetry. The room temperature Raman spectrum also confirmed the formation of crystalline CIS. Solid WZ-CIS samples showed a band gap of 1.40 eV as revealed by UV-Visible diffuse reflectance spectroscopic analysis. Doping of non-magnetic Ga3+-ion and magnetic Fe3+-ion for the In3+-ion in the WZ-CIS has been examined by reacting the sulfate salts of gallium and iron with [Cu(tu)3]Cl and In2(SO4)3. FE-SEM-EDX and TEM-EDX analyses confirmed the presence of gallium and iron in CIS samples. 3.5 at% gallium doped CIS sample showed WZ to be the major phase with few reflections appearing due to the chalcopyrite phase in both the PXRD and TEM-SAED patterns. On doping CIS with 20.8 at% of iron, the hexagonal symmetry of the CIS changed to either cubic (zincblende) or tetragonal (chalcopyrite) depending on the experimental conditions. The tetragonal symmetry of the iron doped CIS has also been verified from TEM-SAED patterns. Introduction of intermediate states in the bandgap of CIS has been observed on doping with iron in the UV-visible diffuse reflectance spectrum with the estimated band gap of 1.05 eV. From magnetization measurements at room temperature, Fe3+-doped CIS showed paramagnetic behavior with χg of 5.89 × 10−6 emu/g. Also, they showed transitions between the defect levels resulting in intense photoluminescence (PL) emission at 750 nm on excitation with λ = 500 nm. The electron paramagnetic resonance (EPR) spectrum confirmed the presence of Fe3+ ions in the CIS lattice exhibiting a broad signal at g = 1.90. The versatility of using this rapid and scalable synthetic approach has been extended to produce orthorhombic AgInS2.

Synthesis of wurtzite CuInS2 nanowires by Ag2S-catalyzed growth

We have demonstrated that wurtzite CuInS2 nanowires could be synthesized in solution via Ag2S-catalyzed growth. It is confirmed that Ag2S nanocrystals are formed firstly and act as catalysts for the growth of the CuInS2 nanowires by monitoring the structures and morphologies of the Ag2S nanocrystals and CuInS2 nanowires during the growth. It is believed that the high mobility of Ag+ promotes the generation of Ag+ vacancies in Ag2S, facilitating the diffusion of Cu and In species from solution into Ag2S to reach supersaturated states. The primary investigation of the optoelectronic property indicates that as-synthesized wurtzite CuInS2 nanowires have enhanced photoresponsivity. Furthermore, this facile method could open a new way to synthesize other various nano-structured ternary and quaternary semiconductors, such as CuInxGa1−xSe2, for applications in solar cells and other fields.

Controlled synthesis of CuInS2, Cu2SnS3 and Cu2ZnSnS4 nano-structures: insight into the universal phase-selectivity mechanism

Well-shaped CuInS2 nanopyramids and nanodisks were synthesized by a wet-chemical method. The phase structure was controlled by the coordination strength between solvent and metal precursors. Zincblende CuInS2 structure was obtained when copper iodide, indium acetate and 1-dodecanethiol were heated at 220 °C in 1-octadecene (ODE) or oleic acid (OA). When the solvent was replaced by oleylamine (OLA) or trioctylphosphine oxide (TOPO), the thermodynamically metastable wurtzite phase was obtained. Interestingly, zincblende phase can also be synthesized in OLA solvent by injecting 1-dodecanethiol into the reaction solution at 315 °C. It was demonstrated that the CuInS2 phase structure selectivity was determined at the initial formation step of a CuIn(SR)x intermediate. An intermediate with high crystallinity will give metastable wurtzite CuInS2 structure, while a low crystallinity intermediate transforms into zincblende CuInS2 phase. This understanding of the crystal formation mechanism enabled us to extend the same synthetic method to another two attractive nanomaterials, Cu2SnS3 and Cu2ZnSnS4. In this work, Cu2SnS3 and Cu2ZnSnS4 nanocrystals with zincblende or wurtzite structures were readily synthesized using similar reaction conditions to CuInS2 nanocrystals.

Wurtzite CuInS2 and CuInxGa1−xS2 nanoribbons: synthesis, optical and photoelectrical properties

Single crystalline wurtzite ternary and quaternary semiconductor nanoribbons (CuInS(2), CuIn(x)Ga(1-x)S(2)) were synthesized through a solution-based method. The structure and composition of the nanoribbons were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), the corresponding fast Fourier transform (FFT) and nanoscale-resolved elemental mapping. Detailed investigation of the growth mechanism by monitoring the structures and morphologies of the nanoribbons during the growth indicates that Cu(1.75)S nanocrystals are formed first and act as a catalyst for the further growth of the nanoribbons. The high mobility of Cu(+) promotes the generation of Cu(+) vacancies in Cu(1.75)S, which will facilitate the diffusion of Cu, In or Ga species from solution into Cu(1.75)S to reach supersaturated states. The supersaturated species in the Cu(1.75)S catalyst, Cu-In-S and Cu-In-Ga-S species, start to condense and crystallize to form wurtzite CuInS(2) or CuIn(x)Ga(1-x)S(2) phases, firstly resulting in two-sided nanoparticles. Successive crystallizations gradually impel the Cu(1.75)S catalyst head forward and prolong the length of the CuInS(2) or CuIn(x)Ga(1-x)S(2) body, forming heterostructured nanorods and thus nanoribbons. The optical band gaps of CuIn(x)Ga(1-x)S(2) nanoribbons can be continuously adjusted between 1.44 eV and 1.91 eV, depending on the Ga concentration in nanoribbons. The successful preparation of those ternary and quaternary semiconductor nanoribbons provide us an opportunity to study their photovoltaic properties. The primary photoresponsive current measurements demonstrate that wurtzite CuIn(x)Ga(1-x)S(2) nanoribbons are excellent photoactive materials. Furthermore, this facile method could open a new way to synthesize other various nano-structured ternary and quaternary semiconductors, such as CuInSe(2) and CuIn(x)Ga(1-x)Se(2), for applications in solar cells and other fields.

Synthesis of bullet-like wurtzite CuInS2 nanocrystals under atmospheric conditions

In this work, a facile and low-cost one-pot method was developed to prepare metastable wurtzite copper indium sulfide (CuInS2) nanocrystals (NCs) under atmospheric conditions. When 1-dodecanethiol and oleylamine were used as the mixed solvent, high quality metastable wurtzite CuInS2 NCs were obtained which can stably exist at room temperature. During the CuInS2 NCs formation, oleylamine not only controls the shape and chemical composition of the CuInS2 NCs, but also influences the phase transition of CuInS2 NCs from chalcopyrite to wurtzite. The proposed synthesis strategy may be used as a general process for the synthesis of metastable wurtzite CuInS2 NCs, and the prepared wurtzite CuInS2 NCs ink may have great potential for absorber layer in solar cells.