Improved short-circuit photocurrent densities in dye-sensitized solar cells based on ordered arrays of titania nanotubule electrodes

We report on the synthesis of highly ordered arrays of titania nanotubules and their applications in enhanced photoelectrochemical cells. Ordered arrays of titania nanotubules of ∼120 nm external diameter, ∼100 nm internal diameter, and ∼5 μm length were fabricated on transparent conductive oxide (TCO) glass substrates by sol–gel processes using in-house prepared anodic alumina templates. After thermal bonding and template removal, the resultant nanotubule structures were applied in dye-sensitized solar cells (DSCs). Overall photoconversion efficiency of nearly 4.8% was achieved with Ru-bipyridine dye, N719, and iodolyte liquid electrolyte. This remarkable performance, for electrodes only ∼5 μm thick, is attributed to an unexpectedly high short-circuit photocurrent density of 16 mA/cm² for masked cells and up to 17 mA/cm² for unmasked cells. The enhanced short-circuit photocurrent (J_sc) is attributed to the high surface area (roughness factor ca. 1207) of the nanotubules and thus improved dye adsorption to the electrodes. The improved J_sc is also attributed to the parallel and vertical orientation of the nanostructures and thus to a well-defined electron diffusion path.     

Structure,stability and electrical properties of the La(2−x)SrxMnO4±δ solid solution series

Single phase materials of the La_(2−x)Sr_xMnO_4±δ (0.6 ≤ x ≤ 2.0) solid solution series were prepared via solid state reaction. The structure of each material was examined at room temperature and determined to be tetragonal for all phases examined. An expansion in lattice volume was observed on increasing lanthanum content. The stability and thermal expansion of each member of the solid solution series was determined via the use of in situ high temperature X-ray diffraction. It was found that all materials remained stable up to a temperature of 800 °C. Thermal expansion coefficients were found to be in the region of 15 × 10^− 6 K^− 1 for La_(2−x)Sr_xMnO_4±δ compounds where x > 1.4. The electrical conductivity of each phase was also determined over a similar temperature range with a maximum value of ∼6 Scm^− 1 at 900 °C for the x = 1.8 phase.     

Tuneability of Sm(1 − x)CexFeO3 ± λ perovskites: Thermal stability and electrical conductivity

Trimetallic perovskite oxides, Sm_(1 ? x)Ce_xFeO_3 ± λ (x = 0–0.05), were prepared by thermal decomposition of amorphous citrate precursors followed by calcinations. The material properties of the substituted perovskites were characterized by X-ray diffraction (XRD), X-ray florescence spectroscopy (XRF), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The doped materials exhibited a single perovskite phase in air up to 1350 °C and have specific surface areas in the range of 2.696–8.665 m²/g. In reducing atmosphere (5%v/vH₂/N₂), the unsubstituted perovskite (x = 0) decomposed into two phases while the ceria stabilized materials (x = 0.01, x = 0.03, x = 0.05) remained in a single phase as revealed by XRD analysis. Their conductivities were measured by the four point probe method in air and in dilute hydrogen (5%v/vH₂/N₂) separately. The ceria substituted materials show increased stability versus reduction and phase separation for a wide temperature range (up to 1000 °C). Although undoped SmFeO₃ has higher conductivity under oxidizing conditions than ceria doped SmFeO₃ due its p-type nature, the situation is reversed under reducing conditions. The ceria substituted perovskites (Sm_(1 ? x)Ce_xFeO_3 ± λ, x = 0–0.05) showed higher conductivity in reducing than in oxidizing conditions, suggesting that ceria doping at the A-site has changed the SmFeO₃ from p-type to n-type semi-conducting behavior.     

Theoretical investigation of the electronic structure and structural phase stability of CeGa2 under pressure

Recently, Chandra Shekar et al. (Phys. Stat. Sol. B 241(2004)2893), studied the structural stability of CeGa₂ under high pressure up to ∼32 GPa and reported a structural transition from hexagonal AlB₂-type to omega trigonal-type starting at ∼16 GPa with a volume collapse of ∼6%. The high-pressure omega triginal phase is found to coexist with the parent phase up to 32 GPa. In this paper, we report the results of our band structure calculations on this system as a function of reduced volume by the tight-binding linear muffin–tin orbital (TB-LMTO) method, in order to look into this structural transition and to understand it in terms of changes in its electronic structure. Our calculations indicate a structural transition at ∼30.6 GPa with a volume collapse of 3.5%, in good agreement with the experimental results. The possible mechanism of the phase transition may be due to f→d electron transfer under pressure. The theoretically calculated ground-state properties, namely the lattice parameters and the bulk modulus are also in good agreement with the experimental values.     

Effect of Eu3+ concentration on microstructure and photoluminescence of Sr2SiO4:Eu3+ phosphors prepared by microwave assisted sintering

In this paper, effect of Eu³⁺ doping concentrations on microstructure and photoluminescence of Sr₂SiO₄ phosphors was investigated. The Sr_2?xSiO₄:xEu³⁺ phosphors with x=0.05, 0.1, 0.2, 0.3 were synthesized by microwave assisted sintering at 1200 °C for 60 min in air. X-ray powder diffraction analysis confirmed the formation of pure Sr₂SiO₄ phase without second phase or phases of starting materials irrespective of the adding amount of Eu³⁺. From scanning electron microscopy image, it is found that with more Eu³⁺ ions introduced to Sr₂SiO₄, the shape of the particles is not much different from each other, but the particle size decreases significantly from 1 to 2 μm (when x=0.05) to less than 500 nm (when x=0.3). The emission spectrum was located obviously at 617 nm as the excitation spectrum at λ_ex=395 nm, and it had best emission intensity when x=0.1.     

Effects of Zr impurity on microscopic behavior of Hf metal

Hf metal with ∼ 3 wt% Zr impurity has been reinvestigated by perturbed angular correlation (PAC) spectroscopy using a LaBr₃(Ce)–BaF₂ detector set up to understand the microscopic behavior of this metal with temperature. From present measurements, five quadrupole interaction frequencies have been found at room temperature where both pure hcp fraction (∼33%) with 12 nearest neighbor Hf surrounding the probe ¹⁸¹Hf atom and the probe–impurity fraction (∼33%) corresponding to 11 nearest neighbor Hf plus one dissimilar Zr atom are clearly distinguished. At room temperature, the results for quadrupole frequency and asymmetry parameter are found to be ω_Q=51.6(4) Mrad/s, η=0.20(4) for the impurity fraction and ω_Q=46.8(2) Mrad/s, η=0 for the pure fraction with values of frequency distribution width δ=0 for both components. At 77 K, only 1 NN Zr impurity (∼93%) and pure hcp (∼7%) components have been found with a value of δ ∼ 10% for the impurity fraction. A drastic change in microstructural configuration of Hf metal is observed at 473 K where the impurity fraction increases to ∼ 50% and the pure hcp fraction reduces to ∼ 15% with abrupt changes in quadrupole frequencies for both components. The pure fraction then increases with temperature and enhances to ∼50% at 973 K. In the temperature range 473–973 K, quadrupole frequencies for both components are found to decrease slowly with temperature. Using the Arrhenius relation, binding energy (B) for the probe–impurity pair and the entropy of formation are measured from temperature dependent fractions of probe–impurity and pure hcp in the temperature range 473–773 K. The three other minor components found at different temperatures are attributed to crystalline defects.     

A comparative study of the Ruddlesden-Popper series,Lan+1NinO3n+1 (n = 1, 2 and 3), for solid-oxide fuel-cell cathode applications

A comparative investigation of the much-studied La₂NiO_4+δ (n = 1) phase and the higher-order Ruddlesden-Popper phases, La_n+1Ni_nO_3n+1 (n = 2 and 3), has been undertaken to determine their suitability as cathodes for intermediate-temperature solid-oxide fuel cells. As n is increased, a structural phase transition is observed from tetragonal I4/mmm in the hyperstoichiometric La₂NiO_4.15 (n = 1) to orthorhombic Fmmm in the oxygen-deficient phases, La₃Ni₂O_6.95 (n = 2) and La₄Ni₃O_9.78 (n = 3). High temperature d.c. electrical conductivity measurements reveal a dramatic increase in overall values from n = 1, 2 to 3 with metallic behavior observed for La₄Ni₃O_9.78. Impedance spectroscopy measurements on symmetrical cells with La_0.9Sr_0.10Ga_0.80Mg_0.20O_3−δ (LSGM-9182) as the electrolyte show a systematic improvement in the electrode performance from La₂NiO_4.15 to La₄Ni₃O_9.78 with ∼ 1 Ω cm² observed at 1073 K for the latter. Long-term thermal stability tests show no impurity formation when La₃Ni₂O_6.95 and La₄Ni₃O_9.78 are heated at 1123 K for 2 weeks in air, in contrast to previously reported data for La₂NiO_4.15. The relative thermal expansion coefficients of La₃Ni₂O_6.95 and La₄Ni₃O_9.78 were found to be similar at ∼ 13.2 × 10^− 6 K^− 1 from 348 K to 1173 K in air compared to 13.8 × 10^− 6 K^− 1 for La₂NiO_4.15. Taken together, these observations suggest favourable use for the n = 2 and 3 phases as cathodes in intermediate-temperature solid-oxide fuel cells when compared to the much-studied La₂NiO_4+δ (n = 1) phase.     

Microstructural properties of plasma-enhanced chemical vapor deposited WNx films using WF6–H2–N2 precursor system

A WF₆–H₂–N₂ precursor system was used for plasma-enhanced chemical vapor deposition (PECVD) of WN_x films. We examined the microstructural changes of the WN_x films depending on N₂/H₂ flow-rate ratio and post-annealing (600–800 °C for 1 h). As the N₂/H₂ flow rate was increased from 0 to 1.5, as-deposited WN_x films exhibited various different crystalline states, such as nanocrystalline and/or amorphous structure comprising W, WN, and W₂N phases, a fine W₂N granular structure embedded in an amorphous matrix, and a crystalline structure of β-W₂N phase. After post-annealing above 600 °C, crystalline recovery with phase separation to β-W₂N and α-W was observed from the WN_x films deposited at an optimized deposition condition (flow-rate ratio = 0.25). From this PECVD method, an excellent step coverage of ∼90% was obtained from the WN_x films at a contact diameter of 0.4 μm and an aspect ratio of 3.5.     

Pressure-induced coordination crossover in magnetite; the breakdown of the Verwey–Mott localization hypothesis

Temperature-dependent ⁵⁷Fe Mössbauer spectroscopy to 40 GPa shows that Fe₃O₄ magnetite undergoes a coordination crossover (CC), whereby charge density is shifted from octahedral to tetrahedral sites and the spinel structure thus changes from inverse to normal with increasing pressure and decreasing temperature. A precursor to the CC is a d-charge decoupling within the octahedral sites at the inverse-spinel phase. The CC transition takes place almost exactly at the Verwey transition temperature (T_V=122 K) at ambient pressure. While T_V decreases with pressure the CC-transition temperature increases with pressure, reaching 300 K at 10 GPa. The d electron localization mechanism proposed by Verwey and later by Mott for T<T_V is shown to be unrelated to the actual mechanism of the metal–insulator transition attributed to the Verwey transition. It is proposed that a first-order phase transition taking place at ∼T_V at ambient pressure opens a small gap within the oxygen p-band, resulting in the observed insulating state at T>T_V.     

Influence of substrate temperature on physical properties of sprayed Zn0.85Mn0.15O films

Zn_1−xMn_xO thin films have been synthesized by chemical spray pyrolysis at different substrate temperatures in the range, 250–450 °C for a manganese composition, x = 15%, on corning 7059 glass substrates. The as-grown layers were characterized to evaluate their chemical and physical behaviour with substrate temperature. The change of dopant level in ZnO films with substrate temperature was analysed using X-ray photoelectron spectroscope measurements. The X-ray diffraction studies revealed that all the films were strongly oriented along the (0 0 2) orientation that correspond to the hexagonal wurtzite structure. The crystalline quality of the layers increased with the increase of substrate temperature up to 400 °C and decreased thereafter. The crystallite size of the films varied in the range, 14–24 nm. The surface morphological studies were carried out using atomic force microscope and the layers showed a lower surface roughness of 4.1 nm. The optical band gap of the films was ∼3.35 eV and the electrical resistivity was found to be high, ∼10⁴ Ω cm. The films deposited at higher temperatures (>350 °C) showed ferromagnetic behaviour at 10 K.     

Synthesis and electrical properties of nanocrystalline Ca1 − xEuxMnO3 ± δ (0.1 ≤ x ≤ 0.4) powders prepared at low temperature using citrate gel method

Nanopowders of Ca_1 − xEu_xMnO₃ (0.1 ≤ x ≤ 0.4) manganites were synthesized as a single phase using the auto gel-combustion method. The citrate method shows to be simple and appropriate to obtain single phases avoiding segregation or contamination. The Ca_1 − xEu_xMnO₃ system has been synthesized at 800 °C during 18 h, against the conventional method of mixing oxides used to obtain these materials at higher temperatures of synthesis. The formation reaction was monitored by X-ray diffraction (XRD) analysis and an infrared absorption technique (FTIR). The polycrystalline powders are characterised by nanometric particle size, ∼ 48 nm as determined from X-ray line broadening analysis using the Scherrer equation. Morphological analysis of the powders, using the scanning electron microscope (SEM), revealed that all phases are homogeneous and the europium-substituted samples exhibit a significant decrease in the grain size when compared with the undoped samples. The structure refinement by using the Rietveld method indicates that the partial calcium substitution by europium (for x ≥ 0.3) modifies the orthorhombic structure of the CaMnO₃ perovskite towards a monoclinic phase. All manganites show two active IR vibrational modes around 400 and 600 cm^− 1. The high temperature dependence of electrical resistivity (between 25 and 600 °C) allows us to conclude that all the samples exhibit a semiconductor behaviour and the europium causes a decrease in the electrical resistivity by more than one order of magnitude. The results can be well attributed to the Mn⁴⁺/Mn³⁺ ratio.     

Synthesis and characterization of nanocrystalline HAp powders prepared by using aloe vera plant extracted solution

Nanocrystalline hydroxyapatite (HAp) powders were synthesized by a simple method using aloe vera plant extracted solution. To obtain nanocrystalline HAp, the prepared precursor was calcined in air at 400–800 °C for 2 h. The phase composition of the calcined samples was studied by X-ray diffraction (XRD) technique. The XRD results confirmed the formation of HAp phase. With increasing calcination temperature, the crystallite of the HAp increased, showing the hexagonal structure of HAp with the lattice parameter, a, in a range of 0.9520–0.9536 nm and c of 0.6739–0.6928 nm. The particle sizes of the powder were obtained to be 43–171 nm. The optical properties of the calcined powders were characterized by Raman and FTIR spectroscopies. The Raman spectra showed a main peak of the phosphate vibration mode (ν₁(PO₄)) at ∼963 cm⁻¹ for all the calcined samples. The peaks of the phosphate carbonate and hydroxyl vibration modes were observed in the FTIR spectra for all the calcined powders. The morphology tends to change from a spherical shape to a rod-like shape with increasing calcination temperature as revealed by TEM.     

Ultrasound assisted synthesis of TiO2–WO3 heterostructures for the catalytic degradation of Tergitol (NP-9) in water

TiO₂–WO₃ heterostructures were synthesized at room temperature, ambient pressure, and short reaction time via a sonochemical approach. TEM and EDX images show that the prepared TiO₂–WO₃ heterostructures consist of globular agglomerates (∼250 nm in diameter) composed of very small (<5 nm) dense particles (WO₃) dispersed inside the globules. The observed less intense monoclinic WO₃ diffraction peak (around 2θ = 22° belonging to (0 0 1) plane) and the high intense hexagonal WO₃ diffraction peak (around 2θ = 28° belonging to (2 0 0) plane) in XRD indicate that there may be phase transition occurring due to the formation of intimate bond between TiO₂ and WO₃. In addition, the formation of such new phase was also observed from Raman spectra with a new peak at 955 cm⁻¹, which is due to the symmetric stretching of W = O terminal. The catalytic activity of TiO₂–WO₃ heterostructures was tested for the degradation of wastewater pollutant containing Tergitol (NP-9) by a process combined with ozonation and it showed two-fold degradation rate compared with ozone process alone.     

Microscopic magnetic properties of (V1−xTix)2O3 near the phase boundary of the metal–insulator transition

Magnetic susceptibility (χ) and ⁵¹V NMR have been measured in (V_1−xTi_x)₂O₃ near the phase boundary of the metal–insulator transition. It is established that the transition from antiferromagnetic insulating (AFI) to antiferromagnetic metallic phases near x_c≈0.05 is not quantum critical, but is discontinuous with a jump of the transition temperature. In the AFI phase at 4.2 K, we observed the satellite in the zero-field ⁵¹V NMR spectrum around 181 MHz in addition to the ‘host’ resonance around 203 MHz. The satellite is also observable in the paramagnetic metallic phase of the x=0.055 sample. We associated the satellite with the V sites near Ti, which are in the V³⁺-like oxidation state, but has different temperature dependence of the NMR shift from that of the host V site. The host d-spin susceptibility for x=0.055 decreases below ∼60 K, but remains finite in the low-temperature limit.     

Stishovite and post-stishovite polymorphs of silica in the shergotty meteorite: their nature,petrographic settings versus theoretical predictions and relevance to Earth's mantle

The Shergotty meteorite contains three dense silica polymorphs in distinct petrographic settings: (1) two post-stishovite SiO₂ polymorphs in individual multiphase grains coexisting with glass with nearly labradorite composition, and (2) large individual stishovite grains in shock-melt pockets which also contain the new CAS phase (Calcium-aluminosilicate; CaAl₄Si₂O₁₁; [Phys Earth Planet Interiors 97 (1996) 97; Geophys Abstract 5(2003)] and hollandite structured plagioclase composition. Prismatic and wedge-shaped grains of the original accessory tridymite (or cristobalite) in the Shergotty meteorite were densified during a major impact event on the Shergottite–Nakhlite–Chaissingite (SNC) parent body and inverted either to (1) multiphase assemblages of several post-stishovite polymorphs depicting prominent tweed pattern or to (2) Large homogeneous stishovite grains in melt pockets. In the first setting we identified an orthorhombic and a monoclinic post-stishovite silica polymorph, respectively. TEM investigations of a grain containing the orthorhombic polymorph revealed an α-PbO₂ like phase that could be assigned to either Pnc2 (with the cell parameters: a=4.55±0.01 Å, b=4.16±0.03 Å, c=5.11±0,04 Å), or Pbcn space group and dense SiO₂ glass. The X-ray diffraction pattern from a second grain revealed a polymorph with a monoclinic lattice with the space group P21/c, that is related to the baddeleyite (ZrO₂) structure with the cell parameters: a=4.375(1) Å, b=4.584(1) Å, c=4.708(1) Å, β=99.97(3), ρ=4.30(2) g/cm³. TEM-SAED pattern of this grain revealed the presence of the α-PbO₂-like SiO₂ polymorph, stishovite, secondary cristobalite, and dense silica glass. The coexistence of several high-density polymorphs and dense silica glass in the same grain suggests that several post-stishovite phases were formed during the shock event in Shergotty. Some of these polymorphs were highly unstable and vitrified, presumably in the decompression stage. Based on diamond anvil experiments on cristobalite a peak shock pressure in excess of 40 GPa could be deduced. The petrographic setting and texture of the single stishovite grains in the melt pockets is different. The mono-phase individual grains occur exclusively as large (>10 μm) rounded objects inside melt pockets together with hollandite structured plagioclase composition and the new CAS phase [1]. Stishovite in melt pockets is barren of any sign of a tweed pattern and contains no silica glass. This suggests that the mechanisms of phase transitions were different in the two lithologies. Stishovite in the melt pockets probably did not form by a retrograde transformation from a post-stishovite polymorph.     

Effect of Li-substitution on piezoelectric and ferroelectric properties of (Bi0.92Na0.92−xLix)0.5Ba0.06Sr0.02TiO3 lead-free ceramics

New lead-free ceramics (Bi_0.92Na_0.92−xLi_x)_0.5Ba_0.06Sr_0.02TiO₃ have been fabricated by a conventional ceramic technique and their electrical properties have been studied. X-ray diffraction studies reveal that Li⁺, Ba²⁺ and Sr²⁺ diffuse into the Bi_0.5Na_0.5TiO₃ lattices to form a new solid solution with a pure perovskite structure. The partial substitution of Li⁺ for Na⁺ increases the remanent polarization P_r of the ceramics. Because of the large P_r and low coercive field E_c, the ceramics with x = 0.075–0.125 exhibit excellent piezoelectric properties: d₃₃ = 189–235 pC/N, k_p = 33.6–36.3% and k_t = 51.6–54.3%. The ceramics exhibit relaxor behaviors after the substitution of Li⁺ for Na⁺. Our results also suggest that polar and non-polar phases may coexist in the ceramics at temperatures above the depolarization temperature T_d.     

Synthesis,characterization and magnetic properties of lightly doped La2−xSrxCuO4 (x = 0.04) nanoparticles

Lightly doped La_2−xSr_xCuO₄ (x = 0.04) nanoparticles with different particle sizes have been successfully prepared by a sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared transmission (IR) spectra and superconducting quantum interference device (SQUID) magnetometer. All samples are single phase and have an orthorhombic unit cell. As the particle size reduces, it is found that the IR band at around 685 cm⁻¹ corresponding to the in-plane Cu–O asymmetrical stretching mode shifts to higher frequency and the magnetization exhibits a large enhancement at low temperature. The magnetic susceptibility of all samples follows a modulated Curie law between ∼20 K and ∼100 K and the Curie constant displays a strong dependence on the particle size. It is suggested that as the particle size decreases surface effects should play an important role in the magnetic properties of the nanoparticles.     

Addendum to “Polymorphic phase transition and thermal stability in squaric acid (H2C4O4)” by K.-S. Lee et al. [J. Phys. Chem. Solids 73 (2012) 890]

While a paper mentioned above being published on line, we have become aware of the high-pressure neutron diffraction study of squaric acid (H₂C₄O₄) by C.L. Bull et al. They developed that neutron diffraction experiments could be performed under quasi-hydrostatic conditions to pressures of up to 18 GPa and showed that the tetragonal phase of H₂C₄O₄ was still observed at 14.5 GPa (above the critical pressure of P_c=0.75 GPa at room temperature) beyond the previous pressure limits of 7 GPa. Taking the high-pressure neutron diffraction results into consideration, modified temperature-pressure phase diagram in the paper stated above is reported.     

Bulk and surface properties of ionic salt CsH5(PO4)2

We report a comparative study of transport and thermodynamic properties of single-crystal and polycrystalline samples of the ionic salt CsH₅(PO₄)₂ possessing a peculiar three-dimensional hydrogen-bond network. The observed potential of electrolyte decomposition ≈ 1.3 V indicates that the main charge carriers in this salt are protons. However, in spite of the high proton concentration, the conductivity appears to be rather low with a high apparent activation energy E_a ≈ 2 eV, implying that protons are strongly bound. The transport anisotropy though is not large, correlates with the crystal structure: the highest conductivity is found in the [001] direction (σ_130 °C ∼ 5.6 × 10^− 6 S cm^− 1) while the minimal conductivity is in the [100] direction (σ_130 °C ∼ 10 ⁻⁶ S cm^− 1). The conductivity of polycrystalline samples appears to exceed the bulk one by 1–3 orders of magnitude with a concomitant decrease of the activation energy (E_a ≈ 1.05 eV), which indicates that a pseudo-liquid layer with a high proton mobility is formed at the surface of grains. Infrared and Raman spectroscopy used to study the dynamics of the hydrogen-bond system in single-crystal and polycrystalline samples have confirmed the formation of such a modified surface layer in the latter. However, no bulk phase transition into the superionic disordered phase is observed in CsH₅(PO₄)₂ up to the melting point T_melt ∼ 151.6 °C, in contrast to its closest relative compound CsH₂PO₄.     

Influence of Cu doping on the microstructure,optical properties and photoluminescence features of Cd0.9Zn0.1S nanoparticles

Cd_0.9−xZn_0.1Cu_xS (0≤x≤0.06) nanoparticles were successfully synthesized by a conventional chemical co-precipitation method at room temperature. Crystalline phases and optical absorption of the nanoparticles have been studied by X-ray diffraction (XRD) and UV–visible spectrophotometer. XRD confirms the phase singularity of the synthesized material, which also confirmed the formation of Cd–Zn–Cu–S alloy nanocrystals rather than separate nucleation or phase formation. Elemental composition was examined by the energy dispersive X-ray analysis and the microstructure was examined by scanning electron microscope. The blue shift of absorption edge below Cu=2% is responsible for dominance of Cu⁺ while at higher Cu concentration dominated Cu²⁺, d–d transition may exist. It is suggested that the addition of third metal ion (Cu²⁺/Cu⁺) is an effective way to improve the optical property and stability of the Cd_0.9Zn_0.1S solid solutions. When Cu is introduced, stretching of Cd–Zn–Cu–S bond is shifted lower wave number side from 678 cm⁻¹ (Cu=0%) to 671 cm⁻¹ (Cu=6%) due to the presence of Cu in Cd–Zn–S lattice and also the size effect. The variation in blue band emission peak from 456 nm (∼2.72 eV) to 482 nm (∼2.58 eV) by Cu-doping is corresponding to the inter-band radiation combination of photo-generated electrons and holes. Intensity of red band emission centered at 656 nm significantly increased up to Cu=4%; beyond 4% it is decreased due to the quenching of Cu concentration.