Cu3BiS3 Thin Films Research Articles

Synthesis of wittichenite Cu3BiS3 thin films by sulfurizing thermally evaporated Cu-Bi metallic stacks

Wittichenite Cu3BiS3 thin films have received significant interest as light harvesters owing to their suitable optoelectronic properties and presence of earth-abundant, and non-toxic elements. We have synthesized Cu3BiS3 thin films by a two-stage process; in which, Cu/Bi/Cu metallic stacks were thermally evaporated and then sulfurized at 400 o C for 10–60 min in a quartz tubular furnace. The influence of sulfurization time on the structural, microstructural, compositional, optical, and electrical properties of the films was investigated. The results revealed that the films were orthorhombic Cu3BiS3 with the following lattice parameters: a = 0.768 nm; b = 1.043 nm; and c = 0.674 nm. Films uniformity, compactness, and crystal grain size increased upon increasing the sulfurization duration. On increasing the sulfurization time, the elemental stoichiometry of the films improved, and the direct optical bandgap increased from 1.38 to 1.40 eV. Additionally, Cu3BiS3 films exhibited p-type electrical conductivity and the electrical resistivity decreased with the increasing sulfurization time. Consequently, the Cu3BiS3 films synthesized at 30- and 60-min sulfurization durations can be applied to thin-film solar cells.

Two-stage growth of Cu3BiS3 thin films: Influence of the Cu/Bi ratio

Thin films composed of Cu3BiS3 have shown significant promise as light-harvesting materials because of their suitable optoelectronic properties and abundant, non toxic constituent elements. A large-grained, highly crystalline Cu3BiS3 films is a prerequisite for application of these layers in solar cells. We have grown large-grained, highly crystalline Cu3BiS3 films by a two-stage process via thermally evaporating Cu/Bi/Cu metallic layers and sulfurization at 400 °C for 30 min. The influence of the Cu/Bi ratio on the growth of Cu3BiS3 thin films was investigated by varying the Bi precursor thickness. The Cu/Bi ratio significantly influenced the structural, microstructural, optical, and electrical properties of Cu3BiS3 thin films. The Cu3BiS3 film synthesized with a Cu/Bi ratio of 4.35 contained Cu1.8S spurious phase, a non-uniform grain morphology, a direct optical bandgap of 1.41 eV, and an electrical resistivity of 75.5 Ωcm. Upon decreasing the Cu/Bi ratio from 3.38 to 2.77, the Cu1.8S spurious phase was eliminated, and phase-pure Cu3BiS3 was crystallized with a uniform grain morphology, particle size of 2–4 μm, direct bandgap of 1.42 eV, and electrical resistivity of 53.5 Ωcm. A further decrease in the Cu/Bi ratio from 2.77 to 2.54 resulted in a slight decrease in the grain size and electrical resistivity of the Cu3BiS3 films. This study demonstrates that Cu3BiS3 films synthesized with near-stoichiometric composition possess better structural, microstructural, optical, and electrical properties than those synthesized with Cu-rich composition and are suitable for use as solar cell absorber layer.

Characterization of CusBiS3 thin films annealing layers of BizS3-CuS chemically deposited

Cu3BiS3 thin films with values of thickness 170 nm were obtained; these films were characterized using X-ray diffraction, Electron Microscopy Scanning, UV-Vis spectrophotometry, and photoconductivity. We obtained values of bang gap energy 1.65 eV and electrical conductivity approximately 2.58 ( Ω-cm)-1. A second layer of Cu3BiS3 was deposited over the first one, thickness increased to 450 nm and band gap energy was 1 eV and electrical conductivity approximately 1 ( Ω-cm)-1.

Research on the Influence of the Interfacial Properties Between a Cu3 BiS3 Film and an Inx Cd1- x S Buffer Layer for Photoelectrochemical Water Splitting.

The ternary compound photovoltaic semiconductor Cu3 BiS3 thin film-based photoelectrode demonstrates a quite promising potential for photoelectrochemical hydrogen evolution. The presented high onset potential of 0.9 VRHE attracts much attention and shows that the Cu3 BiS3 thin films are quite good as an efficient solar water splitting photoelectrode. However, the CdS buffer does not fit the Cu3 BiS3 thin film: the conduction band offset between CdS and Cu3 BiS3 reaches 0.7eV, and such a high conduction band offset (CBO) significantly increases the interfacial recombination ratio and is the main reason for the relatively low photocurrent of the Cu3 BiS3 /CdS photoelectrode. In this study, the Inx Cd1- x S buffer layer is found to be significantly lowered the CBO of CBS/buffer and that the In incorporation ratio of the buffer influences the CBO value of the CBS/buffer. The Pt-TiO2 /In0.6 Cd0.4 S/Cu3 BiS3 photocathode exhibits an appreciable photocurrent density of ≈12.20mA cm-2 at 0 VRHE with onset potential of more than 0.9 VRHE , and the ABPE of the Cu3 BiS3 -based photocathode reaches the highest value of 3.13%. By application of the In0.6 Cd0.4 S buffer, the Cu3 BiS3 -BiVO4 tandem cell presents a stable and excellent unbiased STH of 2.57% for over 100 h.

Potential Effect on the Properties of Cu3BiS3 Thin Film Co-electrodeposited in Aqueous Solution Enriched Using DFT Calculation

Potential Effect on the Properties of Cu3BiS3 Thin Film Co-electrodeposited in Aqueous Solution Enriched Using DFT Calculation

Optoelectronic, structural and morphological analysis of Cu3BiS3 sulfosalt thin films

Sulfosalts are well known naturally occurring mineral species since the surprise mineralogy and are well reported for a variety of applications including photovoltaics. In the current study Cu3BiS3 (wittichinite mineral), a member of the sulfosalt family was crystallized by a simplified route through chemical bath deposition. To elaborate the experimental design and deposition mechanism and for the sake of comparison, Bi2S3 thin films were also deposited. X-Ray Diffraction, Scanning Electron Microscopy, Atomic Force Microscopy, UV–Vis Spectroscopy, and the Hall effect were used to explore the structural, morphological, and optoelectronic behaviour of synthesized materials in the form of thin films. The thickness of the films was measured by ellipsometry. XRD analysis confirmed the Bi2S3 for the first bath, while for the rest of the films Cu3BiS3 phase emerged. Optical bandgap values of 1.0 eV and 1.25 eV were achieved for Bi2S3 and Cu3BiS3 thin films respectively. Results revealed that Cu3BiS3 thin films deposited for 6 h at room temperature demonstrated Hall mobility of 34.9 cm2 v−1 s−1, the charge carrier concentration of 6.07 × 1016 cm−3 and 7.22 O-cm resistivity with the thickness of 126 nm, hence validating the potential of synthesized materials for photovoltaic applications.

Visible light-driven H2O2 synthesis by a Cu3BiS3 photocathode via a photoelectrochemical indirect two-electron oxygen reduction reaction

In this study, a flat and uniform polycrystalline Cu3BiS3 (CBS) thin film was prepared on a molybdenum-coated glass (Mo-SLG) by spray pyrolysis deposition for generation of hydrogen peroxide (H2O2). The dense structure of the film promoted charge transmission, and the combination of the p-type CBS and n-type semiconductor In2S3 deposited by the chemical bath method improved the electron-hole separation efficiency, resulting in a significantly enhanced photocurrent. Deposition of Au nanoparticles reduced the required free energy for oxygen reduction reaction (ORR), improving the selectivity from O2 to H2O2. The photoelectrochemical (PEC) synthesis proceeds by an indirect 2e− ORR initial formation of superoxide, which is disproportionated to H2O2. In the presence of oxygen and visible light, Au-In2S3/CBS could be used to synthesize H2O2 (5.5 mg·L−1·h−1·cm−1) with good Faraday efficiency (71%). This study provided a practical strategy for designing a highly efficient photocathode to produce H2O2 based on improvement in electron-hole transmission efficiency and product selectivity.

Co-electrodeposition of Cu3BiS3 thin films in weakly alkaline aqueous solutions for photovoltaic application

Co-electrodeposition of Cu3BiS3 thin films in weakly alkaline aqueous solutions for photovoltaic application

Photoelectrochemical and photovoltaic cell performances of thermally evaporated Cu3BiS3 thin films

Photoelectrochemical cell and solar cell applications of Cu3xBi2-xS3 thin film with various ‘x’ values (x = 0, 0.25, 0.50, 0.75 and 1) are studied in the present investigation. Phase pure orthorhombic structured Cu3xBi2-xS3 (x = 1) is confirmed from the structural analysis. All the films have higher optical absorption in the visible region and the bandgap values are ranging from 2.26 eV to 1.81 eV for Cu3xBi2-xS3 (x = 0 to 1) films. Morphological analysis showed the uniform distribution of spherical shaped particles of Cu3xBi2-xS3 over the substrate. AFM analysis indicates decrease in surface roughness with increase of ‘x’ values. Electrical studies carried out using Hall effect analysis confirms ‘p’ type conductivity of Cu3BiS3. The photoconversion efficiency through the photoelectrochemical cell performance (PEC) of FTO/Cu3xBi2-xS3 (x = 0.25 to 1) films and solar cell behavior of FTO/Cu3xBi2-xS3 (x = 0.25 to 1)/CdS/Ag devices are reported.

Theoretical evaluation of emerging Cd-free Cu3BiS3 based solar cells using experimental data of chemically deposited Cu3BiS3 thin films

The present research involves a combined experimental and theoretical study to evaluate the optoelectronic properties of Cu3BiS3 (CBS) semiconductor as an effective solar absorber in thin film photovoltaics. Our study consists of the synthesis and characterization of CBS films, followed by the execution of performance analysis as absorber material in a single heterojunction solar cell using numerical simulation by loading the individual material parameters for each layer of CBS solar cell into SCAPS-1D software. In the case of CBS layer, we considered the physical properties of CBS obtained experimentally in this work. The active layer was obtained by thermal diffusion of chemically deposited Bi2S3/CuS binary stacks at 300 °C and 350 °C in an inert atmosphere. Energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy studies confirm the appropriate composition as well as the formation of well-crystalline and single-phase orthorhombic Cu3BiS3 structure. Promising electrical properties were revealed by Hall effect measurements. The performance of the CBS layer was investigated considering the traditional CdS buffer layer and a Cd-free buffer layer such as Bi2S3. The higher conversion efficiency of 7.6% was obtained for CBS/Bi2S3 heterostructure compared with 6.8% efficiency using CdS buffer. A suitable band alignment at the CBS/Bi2S3 interface and ohmic back contact at Mo/CBS junction resulted to be mainly responsible for the enhanced efficiency.

Effects of thiourea dosage on the structural, optical and electrical properties of one-step solution processed Cu3BiS3 film for photovoltaics

Recently, Cu3BiS3 has emerged as an attractive photovoltaic material with low cost and excellent light absorption. However, its device application is still hindered by relatively poor material quality. Here, a one-step solution method based on dimethyl sulfoxide (DMSO) and thiourea (TU) was used to prepare Cu3BiS3 thin films. The effects of TU dosage on the structural, optical and electrical properties of Cu3BiS3 were systematically discerned. The obtained Cu3BiS3 shows the band gap ranging from 1.40 to 1.68 eV and the carrier concentration in the order of 1016 cm−3. Although a stoichiometric overdose of TU was usually applied in preparing high-quality chalcogenide semiconductor films, our results illustrate that properly increasing concentration of TU in precursor solution enhances the grain size and carrier mobility, while much higher TU supply tends to deteriorate them. Correspondingly, the efficiency of device with the structure of Mo/Cu3BiS3/CdS/ZnO/ITO/Al exhibits the similar tendency. The best PCE of 0.291% occurs for the precursor solution with TU concentration of 3.0 M, and the corresponding VOC, JSC and FF values are 233 mV, 2.867 mA/cm2 and 43.552%, respectively.

Hierarchical flower-like Cu3BiS3 thin film synthesis with non-vacuum chemical bath deposition technique

Now-a-days, the progress of thin film semiconductor devices such as CdTe, Cu(In,Ga)Se2 has remarkable development in the field of thin film photovoltaics. The toxicity of cadmium and limited availability of indium impose the search for alternative materials. At this juncture, Cu3BiS3 is one of the promising emerging materials with favorable properties like high absorption coefficient and direct bandgap. Furthermore, the entire ingredients essential for Cu3BiS3 synthesis are cost effective, non-toxic and plenteously accessible in the Earth’s crust. In the present work, hierarchical flower-like Cu3BiS3 thin films were effectively synthesized on a glass substrate by non-vacuum chemical bath deposition method. The XRD approves the amorphous nature of hierarchical flower-like Cu3BiS3 thin films. Raman spectrum ensured the pure phase of Cu3BiS3 by major vibrational peaks at 285 and 468 cm−1. Moreover, SEM shows the formation of hierarchical flower-like nanostructure of Cu3BiS3 thin films. Wettability study of Cu3BiS3 thin films exhibited hydrophobic behavior. The absorption coefficient and the optical bandgap of Cu3BiS3 thin films were found to be 105 cm−1 and 1.73 eV respectively. These hierarchical flower-like Cu3BiS3 thin films may be useful as absorbing layer in the photovoltaic solar cell.

Effect of annealing on the properties of Cu3BiS3 thin films deposited via chemical bath deposition

Cu3BiS3 is an absorber material for thin film solar cells with an optimal band gap of 1.10-1.72 eV, high absorption coefficient (>105 cm-1) and abundant constituents. In this paper, the effect of annealing on the properties of chemical bath deposited (CBD) Cu3BiS3 thin films is reported. The annealed Cu3BiS3 thin films were characterized by using the X-ray diffraction (XRD) and Raman spectroscopy. The XRD analysis revealed the formation of polycrystalline Cu3BiS3 thin films with orthorhombic crystal structure at 673K. The average crystallite size as calculated from the Debye-Scherrer’s formula was found to be 22.09 nm for (131) peak. Raman spectra showed a leading peak at 282 cm-1 that is a characteristic of Cu3BiS3.

One–step synthesis of Cu3BiS3 thin films by a dimethyl sulfoxide (DMSO)–based solution coating process for solar cell application

A large–grain and highly crystalline Cu3BiS3 thin film is successfully prepared by a dimethyl sulfoxide (DMSO)–based solution coating process. Without involving post sulfurization, Cu3BiS3 absorber with grain size of ~ 1µm has been achieved via a short-time drying of spin–coated precursor film on a hot plate at relatively low temperatures (< 300°C). Our Cu3BiS3 film exhibits a direct band gap of 1.47eV with high absorption coefficients (~ 7 × 104cm−1). Hall effect measurements reveal a p–type conductivity with hole concentration of ~ 1016cm−3 and mobility of 52.83cm2/(Vs). Moreover, an initial Cu3BiS3 thin film solar cell with the device structure of glass/Mo/Cu3BiS3/CdS/ZnO/ITO/Al is fabricated, achieving a definite conversion efficiency of 0.17%. The mild preparation condition promises great potential of current method in realizing Cu3BiS3 solar cells on temperature-sensitive substrates such as flexible polymer through an energy efficient way. The Cu3BiS3 has thus been presented as a promising absorber material for solar cell applications.

Fabrication of Cu3BiS3 Photocathode for Photoelectrochemical Hydrogen Evolution

Hydrogen production from water using abundant solar light is now an important research subject from viewpoints of usage of renewable energy and environmental issues. Photoelectrochemical (PEC) water splitting utilizing semiconductor electrodes has been studied extensively as a potential means of converting solar energy into chemical energy in the form of H2. Chalcogenide compounds have emerged as a leading class of thin films for photocathodes due to their suitable band gap for solar energy absorption, high photo-absorption coefficients, and usability in the polycrystalline state. Although Cu-chalcogenide photocathodes such as CuInS2,CuGaSe2, CuGa3Se5,(Ag,Cu)GaSe2, and Cu(In,Ga)Se2, show excellent solar-to-hydrogen conversion efficiency, there are many difficulties in largescale production from the viewpoints of low throughput and material utilization because of the limited availably of elements (i.e., In, Ga and Se). It is therefore evident that more research is required to search for alternative inexpensive and earth-abundant materials. Cu3BiS3 is one of the promising chalcogenide compounds for a photovoltaic device due to its ability to absorb visible light (Eg ≈ 1.4–1.7 eV), a high absorption coefficient (>105 cm-1) compared to that of CuInSe2 and Cu2ZnSnS4, and p-type conductivity with a carrier concentration of ~ 2×1016 cm-3 . Moreover, it is made of cheap, non-toxic, earth-abundant elements and can be easily produced on a large scale. We fabricated a Cu3BiS3 thin film by a simple electrodeposition technique on a molybdenum-coated glass substrate to utilize it as a photocathode for PEC hydrogen evolution. The Cu3BiS3 film was composed of dense crystallites with thicknesses of ca. 0.65 μm, and the optical bandgap was estimated to be ca. 1.6 eV. Photoelectrochemical characterization revealed that the Cu3BiS3 film was a p-type semiconductor with a flat band potential of ca. +0.1 V (vs Ag/AgCl at pH 6), which is suitable for water reduction but cannot be used for water oxidation. Deposition of an In2S3 buffer layer, by which effective contact between p-type Cu3BiS3 and n-type In2S3 was formed, resulted in a significant increase in the photocurrent and a large shift of the photocurrent onset to the positive region. H2 evolution under AM 1.5G simulated solar light was demonstrated using the Pt-In2S3/Cu3BiS3 electrode combined with a Pt electrode under an applied bias (0 V vs. RHE).

A comprehensive review on synthesis and characterizations of Cu3BiS3 thin films for solar photovoltaics

Since the last few decades, light-absorbing materials based on CuInGaSe2 (CIGS), CuInS2 (CIS), and CdTe have dominated the research in thin-film solar cells. To fabricate large-scale solar cells from these materials, problems may arise due to limited availability of the constituents, viz. Se, In, Cd, and Te, and the toxicity of some of these elements. Hence, recent research efforts are attentive toward abundantly available non-toxic, larger value of absorption coefficient and non-conventional elements. The Cu3BiS3 having wittichenite orthorhombic structure is one the most promising absorber layer candidates for low-cost thin-film solar cells. It has suitable direct band gap (1.10–1.86 eV), large absorption coefficient (105 cm−1) with composition of earth abundant, and relatively non-toxic and cost-effective constituents. Till now, a majority work was done on the preparation of Cu3BiS3 thin films by various techniques. Therefore, a comprehensive review of recent literature of Cu3BiS3 is urgently required. This paper will review the various techniques that have been used to deposit Cu3BiS3 semiconductor with the hope of new paths for the beginner.

Effect of Annealing Temperature on Flowerlike Cu3BiS3 Thin Films Grown by Chemical Bath Deposition

For widespread application of thin-film photovoltaic solar cells, synthesis of inexpensive absorber material is essential. In this work, deposition of ternary Cu3BiS3 absorber material, which contains abundant and environmentally benign elements, was carried out on glass substrate. Flowerlike Cu3BiS3 thin films with nanoflakes as building block were formed on glass substrate by chemical bath deposition. These films were annealed at 573 K and 673 K in sulfur ambient for structural improvement. Their structure was characterized using Raman spectroscopy, as well as their surface morphological and optical properties. The x-ray diffraction profile of as-deposited Cu3BiS3 thin film revealed amorphous structure, which transformed to orthorhombic phase after annealing. The Raman spectrum exhibited a characteristic peak at 290 cm−1. Scanning electron microscopy of as-deposited Cu3BiS3 film confirmed formation of nanoflowers with diameter of around 1052 nm. Wettability testing of as-deposited Cu3BiS3 thin film demonstrated hydrophobic nature, which became hydrophilic after annealing. The measured ultraviolet–visible (UV–Vis) absorption spectra of the Cu3BiS3 thin films gave an absorption coefficient of 105 cm−1 and direct optical bandgap of about 1.42 eV after annealing treatment. Based on all these results, such Cu3BiS3 material may have potential applications in the photovoltaic field as an absorber layer.

Development of Cu3BiS3 thin films by chemical bath deposition route

Novel nanofibers of wittichenite Cu3BiS3 thin films were successfully developed by use of a simple and low cost chemical bath deposition method. The Cu3BiS3 thin films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy, surface wettability and optical absorption spectra. The XRD shows a formation of wittichenite Cu3BiS3 pure phase of orthorhombic structure. SEM reveals the formation of a network of nanofibers having a large surface area. Raman study shows a major peak at 284 cm−1 and confirms the formation of pure phase of Cu3BiS3. All thin films of Cu3BiS3 were hydrophilic in nature as contact angle of each film is <90°. The direct band gap of the Cu3BiS3 films were found to be 1.56–1.42 eV, indicates Cu3BiS3 has good properties to perform as an absorber layer in solar cell technology.

Synthesis and characterization of thermally evaporated copper bismuth sulphide thin films

Non-toxic copper containing chalcogenides are considered as promising alternate materials for the absorber layer in thin film solar cells and visible-light harvesting devices. In this paper, we reported synthesis of Cu3BiS3 thin films using a two-step thermal evaporation method for the first time. A Cu2S layer of 0.4μm thickness was firstly evaporated onto glass substrate at room temperature, followed by evaporation of a Bi2S3 layer of 0.8μm thickness. The Cu3BiS3 thin films were formed by thermally annealing and diffusing the two evaporated layers in a vacuum furnace. This method resulted in the improved crystallinity and phase purity of the grown Cu3BiS3 films. Effects of annealing temperature on different properties of the fabricated samples were investigated. The obtained low band-gap (1.45eV) and good optical properties such as low transmittance (10–30%) and reflectance (~10%) of the Cu3BiS3 films demonstrated it as a suitable material for the absorber layer of solar cells.

Study of heterostructures of Cu3BiS3–buffer layer measured by Kelvin probe force microscopy measurements (KPFM)

The interface formed between Cu3BiS3 thin films and the buffer layer is a potentially limiting factor to the performance of solar cells based on Al/Cu3BiS3/buffer heterojunctions. The buffer layers of ZnS and In2S3 were grown by co-evaporation, and tested as an alternative to the traditional CdS deposited by chemical bath deposition. From the Kelvin probe force microscopy measurements, we found the values of the work function of ZnS, In2S3, and CdS, layers deposited into Cu3BiS3. Additionally, different electronic activity was found for different grain boundaries (GBs), from studies under illumination, we also found the net doping concentration and the density of charged GB states for Cu3BiS3 and Cu3BiS3/CdS.