Search

Cu2SnS3 (CTS) is expected to be an absorber material for next-generation solar cells because it is composed of nontoxic, low-cost elements and has an absorption coefficient of >104 cm−1. In this study, the effects of sulfurization in tin sulfide (Sn x S y) and S mixed vapors on various properties of CTS were investigated by using a 3-zone tube furnace to suppress carrier recombination at the grain boundaries and control the composition of the CTS. The CTS deposited via sulfurization in S vapor only (1-zone CTS) contained different monoclinic and tetragonal CTS structures. The grain size of the CTS thin films deposited via sulfurization in Sn x S y and S mixed vapors was not increased. On the other hand, crystal structure analysis revealed that the CTS had grown to single-phase monoclinic CTS. The results suggest that precipitation in Sn x S y and S mixed vapors contributes to the growth of monoclinic CTS with suitable power-generation characteristics. This finding is important for realizing high-efficiency CTS-based solar cells. [ABSTRACT FROM AUTHOR]

Cu(In, Ga)Se2 (CIGS) solar cells are recognized as next-generation space technology due to their flexibility, lightweight nature, and excellent environmental stability. However, assessing their radiation durability remains challenging, necessitating thorough exploration for space viability. We conduct proton irradiation field tests with varying dosages at 380 keV. Both irradiated control and Cs-treated CIGS solar cells demonstrate impressive efficiency recovery after undergoing heat-light soaking (HLS), exceeding 97% and 100%, respectively. Interestingly, Cs-treated CIGS exhibits higher radiative emission intensity even under high fluence irradiation, indicating a shielding effect within the Cs-compound that protects the inner CIGS grains. Leveraging the knowledge gained from power-dependence, temperature-dependence PL, and time-resolved photoluminescence (TRPL), valuable insights into radiation damage, such as potential fluctuations and transitions involving donor–acceptor pairs, are obtained. X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectra further verify the formation of Frenkel defect pairs within the CIGS during irradiation. Remarkably, following HLS treatment, the K-edge shifts back to its initial state, implying a reversible defect healing mechanism. The harsh proton irradiation is first conducted on CIGS solar cells that have a power conversion efficiency exceeding 17%. This accomplishment firmly establishes CIGS thin-film solar cells as the iconic choice for space applications. [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]

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]

To improve the quality and obtain single-phase monoclinic Cu2SnS3 (CTS) thin films, precursors, which were deposited by a non-vacuum dual-source fine-channel mist chemical vapor deposition (CVD) process, were annealed by covering them with a soda lime glass (SLG) substrate or other precursors. After annealing with a cover, the annealed precursor showed X-ray diffraction (XRD) peaks attributable only to monoclinic CTS; however, the chemical composition of the annealed precursor covered by other types of precursors deviated from the stoichiometry. The SLG substrate was found to be suitable for the cover, and the annealing temperature dependence of cover annealing on the SLG substrate was investigated. When annealing the CTS thin film at 550 °C, only a single-phase monoclinic CTS was found in the XRD and Raman measurements. The bandgap of the CTS thin film was estimated to be approximately 0.91 eV from the α h ν 2 plots. Thus, the deposition results showed that a Cu-poor CTS thin film suitable for high-efficiency solar cells can be prepared using a non-vacuum process without the sulfurization treatment. [ABSTRACT FROM AUTHOR]

Cu2SnS3 (CTS) thin films were prepared by a dual-source mist chemical vapor deposistion (CVD) method. Cu–Sn and S mist sources were prepared separately, without a vacuum apparatus or sulfurizing process to reduce cost and to prevent exfoliation of the deposited CTS thin film. The hot plate temperature was varied in the range 350–400 ℃, and CTS thin films with a suitable morphology for solar cells were produced at 370 ℃. However, the composition ratio varied significantly upstream and downstream of the mist flow. Moreover, the S/metal ratio for all obtained films was too low, as a result of a temperature drop due to the low-temperature mist flow. Therefore, the effect of reducing the lift gas flow rate for the Cu–Sn mist source on the CTS films was investigated to prevent this temperature drop. Samples fabricated with a reduced lift gas flow rate exhibited showed X-ray diffraction peaks attributed to the (200), ( 1 ¯ 31 ), ( 1 ¯ 33 ), and ( 3 ¯ 33) planes of monoclinic CTS, as well as monoclinic CTS Raman peaks. In addition, the estimated bandgap energy for the CTS thin films was 0.93–0.96 eV, which corresponds to that reported for monoclinic CTS. This indicates that the fabricated samples were monoclinic CTS deposited by dual-source fine channel mist CVD without the need for a sulfurization process. [ABSTRACT FROM AUTHOR]

The fundamental electrical properties of undoped and Sb-induced Cu2SnS3 (CTS) thin films were evaluated. Furthermore, the relationship between defect properties during intentional degradation and thin film/solar cell properties was investigated. The carrier concentration decreased after Sb induction in the CTS film, and the resistivity increased by one order of magnitude. These values were independent of the Sb volume. These results imply that a small quantity of Sb atoms passivates the defects, such as Sb atoms at Sn or Cu sites that compensate for the intrinsic acceptors at Cu vacancies. In addition, the number of defects around the grain boundary tended to decrease with Sb induction because of passivation. The carrier concentration of the CTS layer remained unchanged following proton irradiation at 1 × 1014 cmâˆ'2. Furthermore, the number of defects increased, independent of the Sb induction. [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]

Intrinsic and extrinsic defects around the p–n interface in Cu2SnS3 (CTS) solar cells were evaluated using low-temperature photoluminescence (LT-PL) measurements. The intrinsic defects were investigated based on the PL-dependence of CTS films on the excitation power and temperature. Donor–acceptor pair recombination was observed with shallow acceptors (copper vacancies, VCu) located approximately 18 meV above the valence band maximum and typical donors located 72 and 112 meV below the conduction band minimum (CBM). The PL spectra of various CTS solar cell structures were measured to identify the Cd-related defects formed by Cd diffusion from the CdS layer. A new LT-PL peak was observed at 0.87 eV for the CdS/CTS solar cells, corresponding to D–A pair recombination with Cd on Cu site donors located 62 meV below the CBM. A p–n homojunction may form in CTS by VCu passivation by Cd diffusion and suppressed interface recombination. [ABSTRACT FROM AUTHOR]

Ternary compound Cu2SnS3 (CTS) thin films were synthesized using two simple and non-vacuum processes: chemical spray pyrolysis and rapid thermal annealing (RTA). The crystal quality of CTS films improved and the band tailing, shown in Tauc's plot, tended to vanish after annealing in a nitrogen atmosphere using RTA. Although ethanol was used as a solvent in the spray pyrolysis, the CTS film was not contaminated by carbon and oxygen. The bandgap of CTS was changed via sulfurization. The optimization of the RTA process affected the composition of the CTS thin films, modifying material defects, and improving the crystal quality. These results represent the initial step toward the practical application of CTS solar cells using an inexpensive fabrication process. [ABSTRACT FROM AUTHOR]

In this work, a comprehensive study on the influences of the various synthesizing parameters of monoclinic Cu2SnS3 using the RF sputtering method, followed by the sulfurization process, is investigated. In particular, the impact of sputtering power and pressure on multi-material target Cu–Sn (compositional ratio Cu:Sn of 52:48%) was examined. All samples exhibited a monoclinic structure with similar split bandgaps around 0.9 eV. Increasing sputtering power showed direct effects on the sputtered Cu/Sn atoms ratio and the secondary phases obtained. The increase of sputtering pressure causes gas droplets and blistering on the film surfaces. The effects of changing the sulfurization temperature and the sulfur powder amount were also studied. The increase in the sulfurization temperature reduces the surface roughness, increases film crystallinity, and minimizes Cu-based secondary phases. The sulfur amount used during the sulfurization process showed a vital impact on film formation. Using a small amount of sulfur produced a partially sulfurized film that exhibited a poor performance solar cell. A power conversion efficiency of 1.94% is achieved with the optimized condition for the bare Cu2SnS3 without doping or heat treatment for the fabricated cell. [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]