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.

One of the intermediate steps in the organo-colloidal synthesis of crystalline Sb 2 S 3 is a synthesis of spherical amorphous Sb 2 S 3 . In order to prove that the synthesized semiconductor can be considered an absorbing material for a solar device, the electronic and photovoltage properties of the amorphized and polycrystalline Sb 2 S 3 thin films deposited by synthesized amorphous nanoparticles were studied. Optical studies revealed that the direct band gap energy was 1.65 eV and, two direct allowed transition of 1.57 and 1.91 eV for polycrystalline and amorphized thin films, respectively. The PL spectra of Sb 2 S 3 showed an emission peak at 1.65 eV for both films.In order to obtain current-voltage (I-V) characteristics, two cells based on the Sb 2 S 3 thin films as both an absorbing material and an electrolyte were designed and made. The observed Sb 2 S 3 thin films, with a thickness of around 10 lm, are of p-type. The exponential growth of the I-V curves reveals that the cells can work as a generator of electricity.

Recently, we have reported the synthesis and optical and electronic properties of Sb 2 S 3 nanowires with small band gap. In order to prove that the synthesized nanowires can be considered as a candidate material for solar cells and in order to obtain I-V characteristics, two very simple cells based on synthesized Sb 2 S 3 nanowires/natural dye composite were fabricated. Exponential growth of the I-V curves after illumination revealed that the cells could work as electricity generators. A better current response was observed for the cell made of synthesized powder with smaller band gap. The efficiency of the cells is quite low, but this was an attempt to create a solar cell in order to better understand the properties of the synthesized Sb 2 S 3 semiconductor and the processes that occur in the cell.

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