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Cu2Sn1-xGexS3 (CTGS) is a compound composed of relatively abundant elements in the crust of the earth. The band gap of CTGS can be tuned by substituting elements at the Sn and Ge sites, making it an attractive material for low-environmental-impact solar cells. In this study, CTGS thin films were fabricated with a controlled [Ge]/([Ge] + [Sn]) composition ratio (x) by combining the co-evaporation method and sulfurization in an infrared furnace. Furthermore, the effect of Na on the CTGS and changes in the solar cell properties were investigated by stacking and sulfurizing NaF on the precursor fabricated using the co-evaporation method. As a result, CTGS with varying x was successfully fabricated by varying the deposition time of the Cu2GeS3 layer using co-evaporation. Additionally, CTGS prepared by doping with Na showed enlarged CTGS crystals compared to Na-free CTGS. The fabricated CTGS solar cells achieved a power conversion efficiency of more than 4.5% after doping with Na. [ABSTRACT FROM AUTHOR]

As a first step toward the realization of high-efficiency Cu2(Sn1-xGex)S3 (CTGS) solar cells, this study investigates the effects of the growth process, focusing on the crystalline structure and morphology of CTGS films formed via different growth processes. These processes include the sulfurization of the Ge/Cu/Sn-S precursor; sulfurization of Cu2SnS3 (CTS) with S and germanium sulfide (GeS) vapor; and co-evaporation of Cu, Sn, Ge, and S. The CTGS films obtained by sulfurization of the Ge/Cu/Sn-S precursor consistently exhibited the largest grain sizes. However, the surface roughness of CTGS films increased with increasing x ratio. Conversely, the CTGS films obtained by the re-sulfurization of CTS films previously formed in S and GeS mixed vapor exhibited both a large grain size and flat surface roughness, rendering them suitable for forming the p-n interface in a solar cell. Therefore, the re-sulfurization of CTS films previously formed in S and GeS mixed vapor is key for achieving high-efficiency solar cells. [ABSTRACT FROM AUTHOR]

In this study, as a novel approach to thin-film solar cells based on tin sulfide, an environmentally friendly material, we attempted to fabricate (Ge, Sn)S thin films for application in multi-junction solar cells. A (Ge0.42 Sn0.58)S thin film was prepared via co-evaporation. The (Ge0.42 Sn0.58)S thin film formed a (Ge, Sn)S solid solution, as confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses. The open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of (Ge0.42 Sn0.58)S thin-film solar cells were 0.29 V, 6.92 mA/cm2, 0.34, and 0.67%, respectively; moreover, the device showed a band gap of 1.42–1.52 eV. We showed that solar cells can be realized even in a composition range with a relatively higher Ge concentration than the (Ge, Sn)S solar cells reported to date. This result enhances the feasibility of multi-junction SnS-system thin-film solar cells. [ABSTRACT FROM AUTHOR]

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]

The effects of Ag in (Cu1–xAgx)2SnS3 (CATS) were investigated in terms of photoluminescence (PL) lifetime, carrier concentration, and solar cell performance with varying Ag/(Cu + Ag) ratios, x. The PL lifetime of CATS solar cells had a maximum value when x was within 7%. A similar tendency was observed for other parameters of the CATS thin films and solar cells. One of the reasons for this is that the number of non-radiative recombination centers in the CATS layer is suppressed by the sulfurization process with Ag. Therefore, even if the Ag content changes slightly in the 0%–11% range, the crystal quality is changed in CATS, resulting in a significant effect on the properties of solar cells. These investigations on the characterization and device physics can be applied to improve the efficiency of CATS solar cells. [ABSTRACT FROM AUTHOR]

Temperature‐dependent optical absorption spectra from transmittance and reflectance measurements of Cu2SnS3 (CTS) thin films which are promising material for solar cells were investigated. Thin film CTS samples with Cu‐poor, near‐stoichiometric, and Cu‐rich compositions were prepared on glass substrates by thermal co‐evaporation and sulfurization. At low temperature, three band‐to‐band (BB) transitions that are allowed between triple upper valence bands and a single lower conduction band were observed for all samples. The square of the product of the absorption coefficient and the photon energy was plotted to estimate the band gap energy for three bands of the Cu‐poor sample. On the other hand, excitonic (EX) transitions that corresponded to three bands were observed for the Cu‐rich and near‐stoichiometric samples. Temperature‐dependent optical absorption spectra with the triple BB and EX transitions were resolved using a simplified fitting equation with Lorentzian functions as the EX transitions. The band gap, EX transition, and exciton binding energies for the lowest energy band of the Cu‐rich sample were determined to be 0.945 eV, 0.936 eV, and 8.9 meV at 6 K, respectively. In the low‐temperature region, anomalous blue‐shifts of the estimated band gap energy with increasing temperature were obtained for three bands of all samples. [ABSTRACT FROM AUTHOR]

Cu2Sn1 −xGe xS3 (CTGS) thin films were prepared by co-evaporation of Cu, Sn, and S to form Cu2SnS3 (CTS) precursors, which were then annealed at 570 °C in an atmosphere composed of N2, GeS2, and S vapor. The films were then used to fabricate photovoltaic cells with the structure glass/Mo/CTGS/CdS/ZnO:Al/Al. A cell with a film composition of Cu2(Sn0.86Ge0.14)S3 fabricated from slightly Cu-rich CTS (Cu/Sn = 2.07) exhibited a conversion efficiency of 3.4% and an open-circuit voltage of 0.29 V. The band gap based on the external quantum efficiency was estimated to be approximately 1.0 eV. The open-circuit voltage was found to be larger than that for a CTS thin film solar cell and increased with band gap energy. [ABSTRACT FROM AUTHOR]

The organic-inorganic hybrid perovskite CH3NH3PbI3 thin-films were obtained by reaction between spin-coated PbI2 precursor thin-films on a porous-TiO2 layer and CH3NH3I vapor. The dependence of the photovoltaic properties of solar cells fabricated with these films on the CH3NH3I powder source temperature and reaction time was investigated. The obtained thin-films were characterized using X-ray diffraction and scanning electron microscopy. The best power conversion efficiencies (PCEs) for each heating condition were 160 °C for 30 min, 150 °C for 45 min, and 140 °C for 60 min. The presence of PbI2 and CH3NH3PbI3 layers, and a flatter and more compact morphology, led to relatively high PCE. The perovskite thin-films were annealed in a N2 atmosphere and the effect of annealing temperature on the photovoltaic performance was also investigated. The PCE for a solar cell fabricated using CH3NH3PbI3 thin-films annealed in the range from 130 to 150 °C for 1 h was over 4%. [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]

Cu2SnS3 (CTS) is a promising compound for use as an absorber layer in thin-film solar cells because it is made up of low-cost and abundant elements. However, the band gap energy of 0.94 eV for monoclinic Cu2SnS3 is less than the optimal value for absorber layers in single-junction solar cells. On the other hand, the band gap energy of Cu2GeS3 (CGS) is approximately 1.5-1.6 eV. Therefore, in this study, we carried out the synthesis of Cu2Sn1− xGe xS3, which is a solid solution of Cu2SnS3 and Cu2GeS3. The structure of the prepared samples was investigated using X-ray diffraction and Raman analyses. Diffuse reflectance spectra were obtained using a UV-Vis-NIR spectrometer and used to estimate the band gap energy. In X-ray diffraction patterns from the synthesized compounds, the diffraction peaks were found to shift to higher 2 θ values with increasing x, indicating a decrease in the lattice constants. In addition, the estimated band gap energy increased from 0.86 to 1.53 eV with increasing x. Cu2Sn1 − xGe xS3 is, therefore, a potential candidate for use as the absorber layer in thin film solar cells because its band gap energy can be adjusted simply by varying its composition. [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]

We have measured photoluminescence (PL) spectra at 10 K for Cu2ZnSnS4 (CZTS) single crystals grown by the iodine transport method and explored the anneal changes of PL spectra under a Zn and S-saturation. All the crystals showed S- and Zn-poor composition, and nearly stoichiometric composition of Cu/(Zn + Sn). The observed PL spectra are divided into two groups; one is PL band with a peak at ∼1.3 eV (1.3-eV band), and another is PL band with a peak at ∼1.35 eV (1.35-eV band). It was found from SEM observations that the 1.35-eV band was observed in crystals with a mirror-like facet and, on the other hand, the 1.3-eV band was seen in the crystals with some small dark areas where the composition is Cu-poor. The Zn-saturated annealing at 600 °C caused the PL peak shift of ∼0.1 eV, from 1.295 to 1.185 eV. The S-saturated annealing at 550 °C caused a disappearance of PL emission. The implications of these annealing behaviour are discussed. [ABSTRACT FROM AUTHOR]

Cu2SnS3 is a promising compound for use as an absorber layer in thin film solar cells because it is made up of low-cost and abundant elements, and has a high optical absorption coefficient. However, the band gap energy of monoclinic Cu2SnS3 is less than the value required for absorber layers in single-junction solar cells. On the other hand, the band gap energy of Cu2SiS3 was reported to be approximately 2.5 eV, which is sufficiently large for this purpose. Therefore, in the present study, an attempt was made to synthesize Cu2Si x Sn1- xS3, which is a solid solution between Cu2SnS3 and Cu2SiS3. In X-ray diffraction patterns from the synthesized compounds, the diffraction peaks were found to shift to higher 2 θ values with increasing x, indicating a decrease in the lattice constants. In addition, the estimated band gap energy increased from 0.85 to 2.56 eV with increasing x. Cu2Si x Sn1- xS3 is therefore a potential candidate for use as the absorber layer in thin film solar cells because its band gap energy can be adjusted simply by varying its composition. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The ternary compound Cu2SnS3 (CTS) is composed of elements that are low in cost, non-toxic, and abundant in the Earth's crust. In addition, CTS is a p-type semiconductor with a high reported absorption coefficient of more than 104 cm−1 and a band gap energy of 0.92-1.77 eV. It is, therefore, considered to be a suitable candidate for the absorber layer in thin film solar cells. In the present study, CTS thin films were produced by first depositing precursor films by co-evaporation of Cu, Sn, and S, and then annealing them. Solar cells were then fabricated using the CTS films as absorber layers, and the dependence of their photovoltaic properties on the annealing temperature was investigated. The solar cell using the CTS thin film annealed at 570 °C exhibited an open-circuit voltage of 248 mV, a short-circuit current density of 33.5 mA/cm2, a fill factor of 0.439, and a conversion efficiency of 3.66%. [ABSTRACT FROM AUTHOR]

The ternary compound semiconductor Cu2SnS3 (CTS) is formed from non-toxic materials that are abundant in Earth's crust and other low-cost elements. CTS has also been reported to a band gap energy range of 0.93-1.77 eV and an absorption coefficient of 1.0×104 cm-1. Consequently, CTS is a potential material for the p-type absorber layer of thin film solar cells. In this study, we examined the dependence of the optical, electrical and photovoltaic properties of CTS thin films on the Cu/Sn composition ratio. CTS thin films were fabricated by sulfurizing evaporated Cu-Sn precursors with different Cu/Sn composition ratios at 560 °C for 2 h in a N2 atmosphere and sulfur vapor. The Cu/Sn composition ratios of the sulfurized films were determined to be 1.6-2.5 by X-ray fluorescence. The solar cell comprising a CTS thin film with a Cu/Sn composition ratio of 1.77 exhibited the best performance among the cells examined, an open-circuit voltage of 242 mV, a short-circuit current density of 28.9 mA/cm2, a fill factor of 41.7% and a conversion efficiency of 2.92% were obtained. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Hydrogen atoms dissolve in Pd at densities up to one H atom per Pd, which provides higher atomic H density than in solid H. They are known to have large diffusion coefficient due to quantum tunneling. Torsional oscillator (TO) technique is employed to investigate the phases of H in Pd, which is known to show phase boundaries at the lowest T among metal-hydrogen (MH) systems. Specific heat measurements have been performed for PdH with x up to high H concentration specimens as well as studies of the resistivity study to establish the unique x− T phase diagram. We have, in addition, been performing TO experiments, in order to study the effect of atomic H intrusion and the dynamics in the PdH(D) system. The TO is a well-established, powerful instrument method to investigate superfluidity and quantum vortices of liquid He, especially in thin films, as well as dislocation dynamics in solids. In our TO experiments on PdH specimens have shown a resonance frequency shift for PdH, with 0.16≤ x≤0.75 at the lowest T's, which can be largely explained by the lattice deformation by H intrusion. This x dependent contribution has a smaller, additional change depending on x and T above ∼50 K. We will show the details of experimental data and discuss the correspondence to the phonon modes change and further possibility of studying occurrence of quantum phenomena for the hydrogen system. [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]

Cu2SnS3 (CTS) contains non-rare metals and it has suitable optical characteristics for the absorber layer of thin-film solar cells. In this study, CTS thin films were fabricated by sulfurizing Cu–Sn precursors deposited by co-electrodeposition. Solar cells with a structure glass/Mo/CTS/CdS/ZnO:Al/Al were fabricated from the films. The best cell had an efficiency of 2.84%. A relatively high conversion efficiency was obtained from films with Cu/Sn≤2. [ABSTRACT FROM AUTHOR]

Cu2SnS3 (CTS) has been reported to have various band gap energies in the range of 0.93–1.77 eV and an absorption coefficient of 1.0×104 cm-1. It consists of elements that are inexpensive due to their abundance in Earth's crust. Consequently, CTS is expected to be utilized in the absorber layers of thin-film solar cells. In this study, Cu/Sn stacked-layer thin-film precursors were deposited on glass and glass/Mo substrates by electron beam evaporation. CTS thin films were fabricated by sulfurizing the precursors at temperatures of 450–580 °C for 2 h in an atmosphere of N2 and sulfur vapor. CTS films were estimated to have band gap energies of 0.96–1.00 eV by extrapolation. A solar cell fabricated using a CTS thin film sulfurized at 580 °C exhibited an open-circuit voltage of 211 mV, a short-circuit current of 28.0 mA/cm2, a fill factor of 0.43, and a conversion efficiency of 2.54%. [ABSTRACT FROM AUTHOR]