Sb2S3 Film Research Articles

Bi doping of Sb2S3 light-harvesting films: Toward suitable energy level alignment and broad absorption for solar cells

Sb2S3 has attracted widespread attention as a photovoltaic absorber material owing to its excellent photoelectric properties. However, the performance of Sb2S3-based solar cells is partly limited by its inappropriate band structure, such as deep valence band maximum (VBM) and wide bandgap, which critically lowers hole extraction efficiency and sets a threshold for attainable short-circuit current density (Jsc). Herein, a cationic bismuth-doping is applied to manipulate the energy level of Sb2S3 film by a hydrothermal process. As a result, the alloyed (Bi,Sb)2S3 delivers a redshift of absorption edge and an upshifted VBM, which are in line with our first-principles calculation. The optimized band structure markedly increases the light-harvesting and hole extraction efficiency. Additionally, the suitable doping of Bi also enhances grain size and preferred [hk1] orientation of absorber layer, consequentially favoring the carrier transport. Finally, this Bi-doping tactic boosts the device efficiency from 3.98 to 5.20% and Jsc from 12.58 to 15.38 mA/cm2 compared with pristine Sb2S3. This work paves an avenue for cationic-doping strategy in Sb2S3 solar cell.

Bi Doped Sb2S3 Thin Film Synthesized by a Two-Step Approach with Enhanced Photoelectrochemical Water Splitting Performance

Photoelectrochemical water splitting (PEC) is believed as a promising approach to address the energy and environmental crisis. Here, we adopted a simple two-step method to synthesize bare Sb2S3 film, and then employed a Bi element doping strategy to improve the PEC performance of obtained bare Sb2S3. The obtained Bi-Sb2S3 exhibited an increased photocurrent density, 2.8 mA cm−2 at 1.23 VRHE and a negative shift of onset potential, compared to bare Sb2S3. The enhancement in PEC performance of Bi-Sb2S3 could be attributed to the expanded light absorption range, increased electron carrier concentration and improved charge transfer ability.

Low‐Cost Fabrication of Sb2S3 Solar Cells: Direct Evaporation from Raw Stibnite Ore

Antimony sulfide is an emerging 1D nontoxic Earth‐abundant photovoltaic material with favorable wide bandgap as a suitable top‐cell candidate for multijunction tandem solar cells. However, the current fabrication technology for Sb2S3 solar cells relies heavily on a high‐purity Sb2S3 source, which limits its large‐scale deployment. Therefore, it is attractive to fabricate the Sb2S3 solar cells directly from the raw stibnite source, which can be cost effective by avoiding the complicated, costly purification and refinement process of the stibnite ore, while reducing process‐emitted pollution. Herein, high‐quality Sb2S3 films (thickness: ≈1 μm) by the vapor transport deposition of raw stibnite ore powder are obtained, followed by a sulfurization process to remove the surface oxides and facilitate alkali element redistribution. In this way, the particle size is increased from ≈500 nm to ≈1.5 μm, the carrier concentration of the Sb2S3 film is increased from ≈1015 to ≈1016 cm−3, and the power conversion efficiency of Sb2S3 solar cell is increased by more than two times. Through the elemental distribution analysis, it is found that it is the redistribution of alkali elements introduced from the natural stibnite ore that induces the grain growth, contributes toward defect suppression, and leads toward enhanced device performance.

Depleted Sb2S3 Thin Film Photoconductive Detectors with Fast Response Speed and High Polarization Sensitivity

AbstractAntimony sulfide (Sb2S3) with high absorption coefficient reveals great potential for photodetectors (PDs) in various fields of military and national economy. A new type of depleted Sb2S3 thin film photoconductive detector by using titanium dioxide (TiO2) interlayer with the structure of Au/(glass/TiO2:)Sb2S3/Au is designed. Compared with normal Au/Sb2S3/Au devices, the depleted Sb2S3 PDs obtain a higher switching ratio of 90, greatly enhancing responsivity and specific detectivity. Owing to the electric field of the depletion region, the response time significantly decreases from 23.2 to 0.6 ms. In addition, the anisotropic Sb2S3 film with [120] dominated horizontal orientation is suitable for polarized light detection. The peak‐to‐valley ratio of the depleted Sb2S3 PD reaches 1.3 at polarized light. The results and methods of this study are expected to expand the application of PDs based on Sb2S3 films.

Solution‐Processed Compact Sb2S3 Thin Films by a Facile One‐Step Deposition Method for Efficient Solar Cells

Antimony sulfide (Sb2S3) is a promising photon‐harvesting material for solar cells. Herein, a facile one‐step deposition method is reported for controllably preparing Sb2S3 nanoparticle films with a preferential [221]‐orientation to a certain extent from a novel precursor solution, formed by dissolving antimony acetate and thiourea in acidified N,N‐dimethylformamide. With titania (TiO2) nanoparticle films as substrates for in situ‐growing Sb2S3 films, the high‐quality Sb2S3/TiO2 planar heterojunction films are obtained for efficient solar cells. The effects of the concentration and [S]/[Sb] molar ratio in the precursor solution on the Sb2S3 film formation and the device performance are investigated. A considerable power conversion efficiency of 5.74% is achieved under AM 1.5G illumination (100 mW cm−2), which is the highest efficiency for the solar cells based on solution‐processed Sb2S3 nanoparticle films by one‐step deposition method without further modification. A promising solution‐processing method is provided to prepare high‐quality Sb2S3 films for efficient solar cells and other optoelectronics.

Performance enhancement in Sb2S3 solar cell processed with direct laser interference patterning

Direct laser interference patterning (DLIP) is used to fabricate large-area, periodic surface patterns on Sb2S3 substrates to enhance the performance of solar cells. Comparing the power conversion efficiencies (PCE) to the reference cell on flat Sb2S3 film, a relative increase of 73% is observed for the DLIP patterned device. Our systematic study reveals that DLIP promotes beneficial crystallization of the Sb2S3 film. Light scattering is increased and recombination is depressed in the textured Sb2S3 film. It is expected that our study can provide a roadmap for the further development of photovoltaic devices (PVs) based on chalcogenide semiconductors.

Manipulating the morphology of CdS/Sb2S3 heterojunction using a Mg-doped tin oxide buffer layer for highly efficient solar cells

Antimony sulfide (Sb2S3) is an appealing semiconductor as light absorber for solar cells due to its high absorption coefficient, appropriate band gap (~1.7 eV) and abundance of constituent elements. However, power conversion efficiency (PCE) of Sb2S3-based solar cells still lags much behind the theoretically predicted due to the imperfect energy level alignment at the charge transporting layer/Sb2S3 interfaces and hence severe charge recombination. Herein, we insert a high-temperature sintered magnesium (Mg)-doped tin oxide (SnO2) layer between cadmium sulfide (CdS) and fluorine doped tin oxide to form a cascaded energy level alignment and thus mitigate interfacial charge recombination. Simultaneously, the inserted Mg-doped SnO2 buffer layer facilitates the growth of the neibouring CdS film with orientation followed by Sb2S3 film with larger grains and fewer pinholes. Consequently, the resultant Sb2S3 solar cells with Mg-doped SnO2 deliver a champion PCE of 6.31%, 22.8% higher than those without a buffer layer. Our work demonstrates that deliberate absorber growth as well as efficient hole blocking upon an appropriate buffer layer is viable in obtaining solution-processed Sb2S3 solar cells with high performance.

Obtaining the solid solution Sb2S3-xSex by selenization of Sb2S3 film and identifying the thermal processing parameters to achieve recrystallization while maintaining phase-purity

In this work, thin films of the ternary material Sb2S3-xSex with promising optical and electrical properties were developed for its application as absorber material in photovoltaic devices. It was found that 400 °C is the lowest recrystallization temperature at which phase-pure polycrystalline films of Sb2S3-xSex can be obtained. Films were recrystallized in a mixture of S/Se vapor by varying the proportion of Se and the film properties were studied as a function of Se content. The conductivity and photosensitivity were increased with the increase in the amount of Se in films. The activation energies associated with the defects or traps in the films decrease with the amount of Se. The morphology of the film changes significantly depending on the annealing pressure. Films recrystallized in an ambient of S/Se vapor generated from 10 mg each of S and Se at 400 °C and 460 Torr pressure are found to have the optimum band gap, highest photosensitivity, and phase-purity. Assuming an appropriate window layer, the modeling result shows that the obtained film Sb2S0.6Se2.4 has the suitable material properties that can result in solar cells with efficiencies in the range of 27%.

Cadmium-free ZnS interfacial layer for hydrothermally processed Sb2S3 solar cells

There is a concomitant interest in reducing carbon footprint and harvesting solar energy with environmentally-friendly materials. In this context, the recent hydrothermal deposition of antimony sulfide is considered promising for low-cost and simple fabrication of photovoltaic devices. However, the need for a CdS film as buffer layer is still a drawback to this approach. In this study, a new strategy by adding a Cd-free ZnS interlayer obtained by successive ionic layer adsorption and reaction method between TiO2 and Sb2S3 film is explored. The structural and morphological characterization of hydrothermally deposited Sb2S3 on TiO2 with and without a ZnS interlayer demonstrate that these films have different crystal orientation and surface morphologies. The champion Sb2S3 solar cell based on ZnS interlayer achieves a power conversion efficiency (PCE) of 5.01%, whereas devices fabricated with pristine TiO2 yields a PCE of 3.42% under similar conditions. Diffusion coefficient, electron diffusion length and interfacial charge recombination measurements show the beneficial effect of adding a ZnS interlayer on the performance properties of hydrothermally processed Sb2S3 solar cells.

Multidentate anchoring through additive engineering for highly efficient Sb2S3 planar thin film solar cells

Sb2S3 is a promising candidate for the flexible solar cells or the top subcells in tandem solar cells due to its wide-bandgap, less toxic, acceptable cost and progressive power conversion efficiency (PCE). However, the poor quality and high trap states of Sb2S3 films limit the device performance further enhancement. Herein, we adopt a multidentate ionic liquid, tetramethylammonium hexafluorophosphate ([TMA][PF6]) as a novel additive to address this issue. The octahedral [PF6]− contains six different oriented fluorine atoms with the lone pair electrons, which could coordinate with Sb atoms due to the multidentate anchoring. Thus, the high-quality Sb2S3 film with low trap states has been achieved. Moreover, the Fermi level of the Sb2S3 film has been upshifted, thereby showing an effective charge transfer. As a result, all photovoltaic parameters of the optimized Sb2S3 devices are obviously enhanced, boosting the final PCE from 4.43 (control device) to 6.83 %. Our study about the multidentate anchoring is manifested to be an effective method to enhance the Sb2S3 device performance.

Solution-Processed All-inorganic Planar Heterojunction Solar Cells by Employing In Situ Grown Interfacial Layer with Dual Functions: Complementary Absorption and Selective Extraction of Photogenerated Holes.

Photovoltaic conversion of renewable solar energy into electricity for sustainable energy production requires efficient, stable, and low-cost solar cells. Developing solution-processed all-inorganic solar cells is a practical scenario in virtue of the high charge mobility and good stability of inorganic semiconductors. Here, for the first time, we present a solution-processed all-inorganic planar heterojunction solar cell based on the nanoparticle film of copper indium sulfide (CuInS2) by using an antimony trisulfide (Sb2S3) nanoparticle film as an interfacial layer between the CuInS2 photon-harvesting layer and cathode. All of the component layers in the solar cell are in a superstrate architecture and sequentially in situ grown on a transparent conducting glass acting as anode by solution-processing methods. The dependences of device performance on the thickness of Sb2S3 film and the reduction of hole-trapping centers in the Sb2S3 film by thioacetamide treatment are investigated. The optimized all-inorganic device exhibits the best power conversion efficiency of 4.85% under AM 1.5G illumination and an excellent thermal stability. It is found that the Sb2S3 interfacial layer sandwiched between the CuInS2 photon-harvesting layer and counter-electrode has dual functions, that is, to provide complementary absorption after CuInS2 attenuation and to act as an effective hole-transporting layer to selectively extract photogenerated holes for effective charge collection efficiency.

Effective additive for enhancing the performance of Sb2S3 planar thin film solar cells

Sb2S3 is a promising photovoltaic absorber with appropriate bandgap, excellent light absorption coefficient and great stability. However, the power conversion efficiency (PCE) of Sb2S3 planar thin film solar cells is unsatisfactory for further commercial application due to low crystallinity and high resistivity of Sb2S3 film. Here, we introduce an additive of 4-Chloro-3-nitrobenzenesulfonyl Chloride (CSCl) to alleviate these problems. The CSCl molecular contains two terminal Cl with lone pair electrons, which have the interaction with Sb atoms. Thus, the Sb2S3 film with enhanced crystallization and low trap states has been obtained and the resistivity is also decreased. Furthermore, CSCl additive raises the Fermi level of the Sb2S3 film, thereby enhancing the transport of electron from Sb2S3 to TiO2. Consequently, the optimal PCE of Sb2S3 solar cells is raised from 4.20% (control device) to 5.84%. Our research demonstrates a novel additive to enhance the photoelectric performance of Sb2S3 solar cells.

Efficient coaxial n-i-p heterojunction Sb2S3 solar cells

Sb2S3 is a kind of emerging light harvesting material for solar cell applications, where both planar and nanostructured configurations are of great interests in the device investigations. This work conducts a comparative study on heterojunction configuration of Sb2S3 solar cells with regard to different CdS substrates. By controlling the hydrothermal durations of Sb2S3 film, the CdS nanorod enables the fabrication of coaxial n-i-p heterojunction Sb2S3 solar cells. It is demonstrated that coaxial heterojunction can effectively improve carrier transport compared with planar heterojunction, leading to the fill factor increasing from 51.3% to 62.7% with regard to different degree of pore filling. Mechanism investigations suggest that both deep-level defect type and defect density in coaxial heterojunction device are significantly reduced, which further reduces carrier recombination in Sb2S3 film, clearly manifesting that the coaxial heterojunction configuration reduces the series resistance and enables efficient carrier transport. In addition, the coaxial heterojunction device presents a remarkably improved stability compared with planar heterojunction device. The research offers a fundamental guideline for the fabrication of efficient antimony chalcogenide solar cells.

Phase change material-based nano-cavity as an efficient optical modulator

Structural phase transition induced by temperature or voltage in phase change materials has been used for many tunable photonic applications. Exploiting reversible and sub-ns fast switching in antimony trisulfide (Sb2S3) from amorphous (Amp) to crystalline (Cry), we introduced a reflection modulator based on metal–dielectric–metal structure. The proposed design exhibits tunable, perfect, and multi-band absorption from visible to the near-infrared region. The reflection response of the system shows >99% absorption of light at normal incidence. The maximum achievable modulation efficiency with a narrow line width is ∼98%. Interestingly, the designed cavity supports critical resonance in an ultrathin (∼λ/15) Sb2S3 film with perfect, broadband, and tunable absorption. Finally, we proposed a novel hybrid cavity design formed of Cry and Amp Sb2S3 thin films side-by-side to realize an optical modulator via relative motion between the incident light beam and cavity. The proposed lithographic free structure can be also used for filtering, optical switching, ultrathin photo-detection, solar energy harvesting, and other energy applications.

Enhancing the efficiency of Sb2S3 solar cells using dual-functional potassium doping

Antimony sulphide (Sb2S3) thin films have attracted considerable research interest as a photovoltaic absorber material owing to their suitable band gap, large absorption coefficient, and excellent photoelectronic properties. In this study, cadmium sulphide (CdS) films were doped with potassium, which increased their crystallinity and optical transmission. These films were then used as a buffer layer to increase the efficiency of Sb2S3 solar cells. Furthermore, the potassium diffused into the Sb2S3 film, which increased their crystallinity and light absorption and decreased its surface roughness. Dual-functional potassium doping helped improve all of the photoelectric parameters of the Sb2S3 solar cells. Specifically, the device efficiency increased from 4.57% to 6.53% (an increase of 42.89%), and a high current density of 15.29 mA cm−2 was achieved. These findings are expected to facilitate the further development of Sb2S3 thin-film solar cells for industrial applications.

Robust formation of amorphous Sb2S3 on functionalized graphene for high-performance optoelectronic devices in the cyan-gap

Despite significant progress in the fabrication and application of semiconductor materials for optical emitters and sensors, few materials can cover the cyan-gap between 450 and 500 nm. We here introduce a robust and facile method to deposit amorphous Sb2S3 films with a bandgap of 2.8 eV. By exploiting the tunable functionality of graphene, a two-dimensional material, efficient deposition from a chemical was achieved. Ozone-generated defects in the graphene were shown to be required to enhance the morphology and quality of the material and comprehensive characterization of the seed layer and the Sb2S3 film were applied to design an optimal deposition process. The resulting material exhibits efficient carrier transport and high photodetector performance as evidenced by unprecedented responsivity and detectivity in semiconductor/graphene/glass vertical heterostructures. (112 A/W, 2.01 × 1012 Jones, respectively).

Synergistic Effect through the Introduction of Inorganic Zinc Halides at the Interface of TiO2 and Sb2S3 for High-Performance Sb2S3 Planar Thin-Film Solar Cells.

The competition between charge recombination and extraction principally affects the fill factor (FF) and power conversion efficiency (PCE) of planar thin-film solar cells. In Sb2S3 thin-film solar cells, the electrocharge recombination and extraction n transport layer (ETL) plays a significant role in electron extraction and determination of Sb2S3 film absorber quality. Herein, a TiO2 ETL is strategically modified using an inorganic salt zinc halide (i.e., ZnCl2, ZnBr2, ZnI2), which simultaneously improves the electronic properties of TiO2 and promotes the growth of Sb2S3 films with larger grain size and higher crystallinity. The experimental results and theoretical calculations further reveal that the zinc halide can interact with TiO2 and simultaneously bond strongly with the upper Sb2S3 film, which creates a unique pathway for electron transfer, passivates the trap states, and alleviates the recombination losses effectively. As a result, an average PCE of 6.87 ± 0.11% and the highest PCE of 7.08% have been attained with an improved FF from 51.22 to 61.61% after ZnCl2 introduction. Additionally, introduction of ZnCl2 helps the unencapsulated devices to maintain 93% of their original performance after 2400 h of storage in a nitrogen-filled glovebox. This work develops an effective route for the optimization of ETLs and defect healing using simple and low-cost inorganic salts.

Controllable orientations for Sb2S3 solar cells by vertical VTD method

AbstractAntimony sulfide (Sb2S3) is a promising photoelectric material because of its wide bandgap approximately 1.7 eV for next‐generation solar cells, high optical absorption coefficient, and its green and earth‐abundant constituents. Different to traditional cubic structure photovoltaic materials, Sb2S3 holds one‐dimensional crystal structure and its thin film with [hk1] preferred orientation shows one‐order‐higher carrier transport mobility. However, all the reported Sb2S3 films exhibited [hk0] preferred orientation on CdS‐based superstrate device structure up to now. Thus, it is indispensable to study the controllable‐orientations Sb2S3 film deposition and the relationship between the orientation and performances. In this paper, we develop a vertical vapor transport deposition (V‐VTD) method, which can tune the preferred orientation of Sb2S3 thin film from [hk0] to [hk1] by reaction recipe monitoring. Combining the experiment results, a reasonable deposition/reevaporation competing model is suggested to explain above orientation conversion mechanism. The device efficiency increases from less than 2% to about 4% with the orientation of Sb2S3 film changing from [hk0] to [hk1]. By fine regulating the technique of deposition, the device with [hk1] orientation has better crystallinity, lower interface recombination, and higher built‐in voltage comparing with the [hk0] one. Finally, a champion power conversion efficiency (PCE) of 4.5% has been achieved, and the VOC of 730 mV is the top value among the Sb2S3 solar cells. The present versatile orientation tuning strategy could overcome the bottleneck of strong anisotropic materials and show high potential for noncubic material deposition and related optoelectronic device performance enhancement.

Current improvement in substrate structured Sb2S3 solar cells with MoSe2 interlayer**Project supported by the National Key R & D Program of China (Grant Nos. 2019YFB1503500, 2018YFE0203400, and 2018YFB1500200), the National Natural Science Foundation of China (Grant No. U1902218), the YangFan Innovative and Entrepreneurial Research Team Project of China (Grant No. 2014YT02N037), and the 111 Project, China (Grant No. B16027).

Sb2S3 solar cells with substrate structure usually suffer from pretty low short circuit current (JSC) due to the defects and poor carrier transport. The Sb2S3, as a one-dimensional material, exhibits orientation-dependent carrier transport property. In this work, a thin MoSe2 layer is directly synthesized on the Mo substrate followed by depositing the Sb2S3 thin film. The x-ray diffraction (XRD) patterns confirm that a thin MoSe2 layer can improve the crystallization of the Sb2S3 film and induce (hk1) orientations, which can provide more carrier transport channels. Kelvin probe force microscopy (KPFM) results suggest that this modified Sb2S3 film has a benign surface with less defects and dangling bonds. The variation of the surface potential of Sb2S3 indicates a much more efficient carrier separation. Consequently, the power conversion efficiency (PCE) of the substrate structured Sb2S3 thin film solar cell is improved from 1.36 % to 1.86 %, which is the best efficiency of the substrate structured Sb2S3 thin film solar cell, and JSC significantly increases to 13.6 mA/cm2. According to the external quantum efficiency (EQE) and C–V measurements, the modified crystallization and elevated built-in electric field are the main causes.

Efficient Antimony‐Based Solar Cells by Enhanced Charge Transfer

AbstractThe main mechanism of most solar cells is that the light produces photogenerated electrons and holes, which are transferred to the electron transport layer and the hole transport layer (HTL), respectively. Then, these holes and electrons are transported to the anode and cathode, respectively, to generate electric current. Thus, charge transfer is a crucial process to fabricate efficient solar cells. Here, a fast vapor process is developed to fabricate SbSI and SbSI‐interlayered Sb2S3 solar cells by annealing an Sb2S3 film and SbI3 powder in an inert gas atmosphere. The charge transfer of the vapor‐processed SbSI solar cells is increased by shortening the path length from SbSI to the HTL. This is achieved by an intimate contact between SbSI and the HTL, which is obtained by optimizing the morphology of SbSI, resulting in a record power conversion efficiency (PCE) of 3.62% in pure SbSI‐based solar cells under standard illumination at 100 mW cm−2. In addition, the charge transfer of the SbSI‐interlayered Sb2S3 solar cells is enhanced by increasing the external driving force, an energetically favorable driving force provided by the TiO2/Sb2S3/SbSI/HTM structure, and the best‐performing SbSI‐interlayered Sb2S3 solar cell exhibits a PCE of 6.08%.