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Cu-doped (as p-doped) and Se-doped (as n-doped) Sb 2 S 3 were synthesized from undoped Sb 2 S 3 using a newly developed technique, simple colloidal synthesis method. X-ray diffraction measurements detected no peaks related to any of the Cu and Se compounds in Cu and Se-doped samples. Energy dispersive X-ray analysis, however, confirmed the presence of Cu and Se ions in the doped samples. Diffuse reflectance spectroscopy revealed the optical band gap energy changes because of doping effect, as reported for both the p-type and the n-type material. The valence-band X-ray photoelectron spectroscopy data showed a significant shift in the valence band to higher (Se-doped; +0.53 eV) and a shift to lower (Cu-doped; À0.41 eV) binding energy, respectively, when compared with the undoped sample. We report here on an inexpensive solar cell designed and made entirely of a synthesized material (indium tin oxide/p-doped Sb 2 S 3 + polyaniline (PANI)/amorphous/undoped Sb 2 S 3 + PANI/n-doped Sb 2 S 3 + PANI/PANI/electrolyte (0.5 M KI + 0.05 M I 2 )/Al). The cell has a high efficiency of 8% to 9% at a very low light intensity of only 5% sun, which makes it particularly suitable for indoor applications. As found, the cell performance at the intensity of 5% sun is governed by high shunt resistance (R SH ) only, which satisfies standard testing conditions. At higher light intensities (25% sun), however, the cell exhibits lower but not insignificant efficiency (around 2%) governed by both the series (R S ) and the R SH . Minimal permeability in the UV region (up to 375 nm) and its almost constant value in the visible and the NIR region at low light intensity of 5% sun could be the reasons for higher cell efficiency.

We report a simple colloidal synthesis of two types of Sb 2 S 3 nanowires with small band gap and high aspect ratio. Field-emission scanning electron and transmission electron microscopies confirmed formation of high aspect ratio Sb 2 S 3 nanowires, separated in the form of bundles and coalesced with each other in long bars. Diffuse reflectance and absorption spectroscopies revealed that the optical band-gap energies of the synthesized nanowires separated in the form of bundles are 1.56 and 1.59 eV, and coalesced with each other in long bars are 1.36 and 1.28 eV, respectively. The structure refinement showed that Sb 2 S 3 powders belong to the orthorhombic structure with space group Pnma (no. 62). It was found that Sb 2 S 3 nanowires separated in the form of bundles predominantly grow along the [0 1 0] direction being in the needle-like shape. The nanowires coalesced with each other in long bars rise in the form of long bars, are ribbon-like in shape and have expressed {1 0 1} facets which grow along the [0 1 0] direction. No peaks in photoluminescence spectra were observed in the spectral range from 250 to 600 nm. In order to shed more light on the experimental results concerning the band-gap energies and, in the literature generally poorly investigated electronic properties of the synthesized material, we performed theoretical calculations of the electronic structure and optical properties of the Sb 2 S 3 samples synthesized here. This was done on the basis of density functional theory with the generalized gradient approximation, and also with an improved version of the exchange potential suggested recently by Tran and Blaha. The main characteristic is the significant improvement of the band gap value.

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We report here on an inexpensive, solid and stable solar cell designed and made entirely of synthesized materials, Sb 2 S 3 / hypericin (dye) thin film on ITO-coated glass (working electrode), aluminum (counter electrode), and PVA matrix (solid carrier) loaded with electrolyte (0.5M KI 1 0.05M I 2 ). The fact that the cell is inexpensive but also stable and solid, with efficiency of around 1.3%/cm 2 at a very low light intensity of only 5% sun, makes it particularly suitable for indoor applications. At higher light intensities of 25 and 55% sun, however, the cell exhibits lower efficiency, around 0.3 and 0.07%/cm 2 , respectively. Development of low-cost cell technology combined with understanding of low light utilization and setting of standard conditions should be some of the future directions the research in this area should follow. Therefore, in this work, we tried to give sufficient reasons for establishing standard conditions related to low light intensity.

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We show that a single geometrical rule underlies the stability of "polyoxomolybdates", the variety of clusters of molybdenum(VI) oxide in (acidified) aqueous solution that are found experimentally. We predict that upon increasing the proton or total molybdenum oxide concentration, the average size of the clusters increases. We compare our predictions with results from ultracentrifugation experiments and with data in the literature. Finally, it is shown that the formation of metal oxide clusters is thermodynamically equivalent to the formation of surfactant micelles.