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Ag8SnS6 (ATS) has been reported to have a band gap of 1.33 eV and is expected to be a suitable material for the light-absorbing layers of compound thin-film solar cells. However, studies on solar cells that use ATS are currently lacking. The objective of this study is to obtain high-quality ATS thin films for the realization of compound thin-film solar cells using vacuum deposition and sulfide annealing. First, glass/SnS/Ag stacked precursors are prepared by vacuum deposition. Subsequently, they are converted to the ATS phase via sulfide annealing, and various process conditions, namely, annealing time, annealing temperature, and number of steps, are studied. By setting the heat treatment temperature at 550 °C and the heat treatment time at 60 min, a high-quality ATS thin film could be obtained. Multi-step heat treatment also produces thin films with nearly no segregation or voids. [ABSTRACT FROM AUTHOR]

The dependence of photoluminescence (PL) on sulfurization temperature of the Cu2SnS3 (CTS) thin films was investigated. CTS thin films were prepared at various sulfurization temperatures in the range of 500–600 ℃, and differences in the conversion efficiency of solar cells with the CTS thin films as absorption layer and the crystal structure of the CTS thin films were observed. In low-conversion-efficiency CTS films, which were a mix of monoclinic and cubic crystals, the PL spectrum only showed donor–acceptor pair (DAP) recombination luminescence due to deep defects. In high-conversion-efficiency CTS thin films, which contained only monoclinic crystals, the PL spectrum showed DAP recombination luminescence originating from the same deep defects. In addition band-edge luminescence was observed at room temperature. Thus, it was found that the conversion efficiency and crystal structure of CTS thin film can be easily estimated from PL measurements. [ABSTRACT FROM AUTHOR]

We investigated the effect of H2S annealing for glass/Ag/Sn and glass/Ag/SnS precursor thin films deposited by vacuum evaporation. The glass/Ag/Sn and glass/Ag/SnS stacked precursors were deposited on soda-lime glass substrates at 300 °C. After the evaporation, the stacked precursors were annealed from 300 to 500 °C for 60 min in H2S atmosphere. A Ag8SnS6 thin films can be prepared with Ag2SnS3 and SnS2 crystals. The grain size of the crystals in the thin films using a glass/Ag/SnS stacked precursor was larger than that using a glass/Ag/Sn stacked precursor. The absorption coefficients and band-gap energy of Ag-Sn-S thin films with Ag8SnS6, Ag2SnS3, and SnS2 crystals were above 104 cm−1 and approximately 1.3 eV, respectively. [ABSTRACT FROM AUTHOR]

The binary compound SnS consists of elements that are non-toxic, inexpensive, and abundant in the Earth's crust. It is a p-type semiconductor with a band gap energy of 1.3 eV and an absorption coefficient of 104 cm−1, and is therefore a potential candidate for use as a solar cell absorber material. In this study, SLG/Mo/SnS/CdS/ZnO:Al/Al and SLG/Mo/SnS/ZnO/ZnO:Al/Al SnS thin-film solar cells with different buffer layers were fabricated using a co-evaporation method. The dependence of the photovoltaic properties of the SnS thin-film solar cells with CdS or ZnO as the buffer layer was investigated. We demonstrate that the device with a ZnO buffer layer exhibited higher conversion efficiency and short-circuit current density compared to the device with a CdS buffer layer. [ABSTRACT FROM AUTHOR]

Cu(In,Ga)Se2 (CIGS) crystals were synthesized by a mechanochemical (MC) process using a crank ball mill. The molar ratios of starting materials were Cu:In:Ga:Se=1:1-x:x:2 (0≤x≤1) and Cu:In:Ga:Se=1:0.7:0.3:y (2≤y≤3). The reaction time reduced with decreasing Se and Ga molar ratios. The collection rate decreased with longer reaction times. From XRD patterns, we confirmed that the CuInSe2 and/or CuGaSe2crystals were successfully grown when the powders reacted. Although the crystals grown with a selenium molar ration of 2 were Se-poor, those grown at a molar ratio of 3 were Se-rich. When Se increasing molar ratio, Cu, In, and Ga were away from the stoichiometric. With a molar ratio of Cu:In:Ga:Se=1:0.7:0.3:2.5∼2.7, their composition became stoichiometric. Crystal morphology was varied. CIGS crystals were thus successfully synthesized using a crank ball mill. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In this work, Cu-Sn-S thin films were prepared from a vacuum-evaporated Cu-Sn precursor via annealing in H2S from 200 to 500 °C for 1 h. Cu2SnS3 thin films with monoclinic and tetragonal structures were observed by X-ray diffraction when the annealing temperature exceeded 325 °C. In addition, the SnS phase was observed when the annealing temperature exceeded 275 °C. The surface of the Cu-Sn-S thin film annealed at 500 °C was uneven due to the re-evaporation of SnS. The absorption coefficient of the Cu-Sn-S thin films was above 104 cm-1 with energies above 1.0 eV. The band gap of these films was estimated from transmission and reflection apectra using UV-visible-NIR spectrophotometry to be between 0.88-1.0 eV when the annealing temperature exceeded 450 °C. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Optical second harmonic generation (SHG) has been studied in TlMeX2 (Me=In,Ga, X=S,Se,Te) compounds with layered and chain crystalline structures. For layered TlInS2 and TlGaSe2, SHG signal has been observed in a range of temperatures below the point of phase transition into ferroelectric phase for which asymmetry is prominent. On the other hand, the chain TlInSe2 and TlGaTe2 have shown SHG signal at a temperature above 270 and 293K, respectively. Both the TlInSe2 and TlGaTe2 have symmetry centre at room temperature and second order optical non-linearity is an artefact incompatible with their bulk structure. Surface structure is speculated to be responsible for SHG signal observed in these materials for the first time to our knowledge. The details of temperature behaviour of SHG in TlInSe2 and TlGaTe2 lead to a phase-transition based model for explanation of the observed phenomenon. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Proton irradiation damage for CuInSe2 (CIS) solar cell material was investigated using piezoelectric photothermal spectroscopy (PPTS) from the viewpoint of nonradiative transition. Three peaks at 1.01, 0.94 and 0.86 eV were observed at room temperature. The peaks at 1.01 and 0.86 eV were attributed to free exciton and the proton irradiation-induced defects, respectively. This is because the 0.86 eV peak appeared after irradiation with the proton energy of 0.38 MeV and a fluence of 1 × 1014 cm-2. Since the irradiation defect was clearly observed at room temperature, we concluded that the PPTS technique was a powerful tool to study the defect level in the irradiated semiconductor thin films. [Copyright &y& Elsevier]

Porous CuInS2 crystals were grown from starting materials CuCl2·2H2O, InCl3·4H2O and thiorea with ethylene glycol solution, that were placed into a flask, heated, and refluxed for 1 hour. The diffraction peaks only from CuInS2 phase appear for all the samples. The morphology of CuInS2 crystal was porous, and the porous crystals exist in two kinds. One kind was flower-like crystals which complexly lack the flakes, another one was sphere-like crystals existed with a number of the poles. The specific surface area of the samples grown by stirring starting materials with In to Cu ratio of 4.3 for 30 minutes was found approximately to be 55 m2/g. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: We characterized AgInS2 thin films prepared by vacuum evaporation. In the case of thin films annealed at 400°C, diffraction peaks were observed only for the chalcopyrite AgInS2 phase. The chemical composition of the thin films annealed at 400°C was 26.5at% Ag, 23.8at% In, and 49.7at% S. PL spectra of the AgInS2 thin films at 10.7K showed peaks at 1.70, 1.80, and 1.83eV. The PL peak at1.80eV was attributed to sulfur deficiency. [Copyright &y& Elsevier]

Electron nonradiative relaxation through the proton-irradiation-induced defects in CuInSe2 solar cell material were investigated by using a piezoelectric photothermal spectroscopy (PPTS). Among the observed three peaks at 1.01, 0.93, and 0.84 eV, it was concluded that the peak at 0.84 eV was due to the proton-irradiation-induced defect. This is because this peak appeared after irradiation with the proton energy of 0.38 MeV and the fluence of 1×1014 cm-2. The peaks at 1.01 and 0.93 eV were attributed to free band-edge exciton and intrinsic defect level, respectively. The intensities for the latter two peaks were not affected by the irradiation. Since the irradiation defect was clearly observed at room temperature, we concluded that the PPTS technique was a very sensitive tool to study the defect level in the irradiated semiconductor thin-film solar cell structures. [ABSTRACT FROM AUTHOR]

(Cu,Ag)2SnS3 thin films and solar cells are prepared by sulfurization of KF/Sn/(Cu + Ag) stacked precursors in a sulfur and tin mixing atmosphere. Their properties are investigated. Stacked KF/Sn/(Cu + Ag) precursors are deposited on Mo/soda lime glass substrate by sequential evaporation of Cu + Ag, Sn elements, and KF. The molar ratios of the evaporation materials are held constant at (Cu + Ag):Sn = 1.0:0.6 and Ag/(Cu + Ag) = 0.05, and the KF/Cu molar ratio is changed from 0 to 0.05. The precursors are crystallized by annealing for 30 min at 570 °C in a sulfur and tin mixing atmosphere. The compositions are approximately constant, and the dependence of the composition ratio on the KF addition quantity is not observed. For all samples, the X‐ray diffraction patterns and the Raman spectra corresponding to CATS are obtained. The values of Voc increased with increasing KF/Cu molar ratio until KF/Cu = 0.03. The best solar cell in this study showed a Voc of 248 mV. [ABSTRACT FROM AUTHOR]

To enlarge the bandgap of Cu2SnS3 (CTS), Ag‐incorporating CTS thin films are successfully deposited by sulfurizing Ag‐Cu‐Sn precursors featuring various Ag contents and the constant Cu/Sn ratio of 1.75, which is the optimal value for CTS thin‐film solar cells. To control the Ag content of the films, the thickness of the Ag layers of the precursors is varied from 0 to 200 nm, which corresponds to the Ag/(Ag + Cu) ratio of the films varying from 0 to 0.32. The films featuring Ag/(Ag + Cu) ratios smaller than 0.16 are solid solutions of CTS and Ag2SnS3, that is, (Cu,Ag)2SnS3 (CATS), while the film featuring the Ag/(Ag + Cu) ratio of 0.32 appears to be a mixture of CATS and Ag‐Sn‐S related crystals, such as Ag8SnS6. The grain size and bandgap increase as the Ag/(Ag + Cu) ratio increases up to 0.16. The highest power conversion efficiency (PCE) of 3.6% is obtained for the cell featuring the Ag/(Ag + Cu) ratio of 0.08. The highest open cell voltage (VOC) for the CATS thin‐film solar cells is obtained to be 0.284 mV. However, the improvement in PCE is attributed to the increase in the short‐circuit current density and fill factor of the cell rather than the increase in VOC. [ABSTRACT FROM AUTHOR]