Thin Film Absorber Layer Research Articles

Effect of carrier gas on copper antimony sulfide thin films by spray pyrolytic approach

This study explores the ternary compound semiconductor as a potential absorber layer for third-generation solar cells. CuSbS2, a promising candidate for thin film absorber layers, is fabricated using a simple spray pyrolysis method. The research specifically investigates the influence of two different carrier gases during the fabrication process. X-ray diffraction as well as Raman studies confirm that the films exhibit a chalcostibite structure. Notably, films fabricated with nitrogen as the carrier gas demonstrate enhanced crystallinity, accompanied by reduced microstrain and dislocation density. Furthermore, these films exhibit a significantly improved absorption coefficient, reaching 105 cm-1 . Optical studies indicate that the materials possess a direct band gap of 1.50 eV and exhibit p-type conductivity. CuSbS2 thin film heterojunction solar cell exhibits a maximum efficiency of 0.49%.

Over 10% efficient Cu2ZnSn(S, Se)4 Thin-Film cells prepared by aluminium doping

Cu2ZnSn(S,Se)4(CZTSSe) solar cell is of excellent development tendency because of lower pollution and outstanding power conversion efficiency(PCE). Yet, current PCE of CZTSSe is limited because of a high open-circuit voltage deficit, primarily put down to severe band tailing and carrier recombination. In this paper, absorber films were obtained by solution method and the influences of different aluminum doping concentrations on the properties of CZTSSe thin film cell were studied. Analysis about X-ray diffraction (XRD) and Raman spectroscopy confirms which Al has incorporated into CZTSSe thin film lattice and replaced Sn. Hall effect measurements reveal the improvement of carrier concentration on thin film absorber layer attribute to the formation of AlSn acceptor defects. Furthermore, X-ray photoelectron spectroscopy (XPS) reveals that Al enter into the CZTSSe lattice and Al is in the appropriate state of + 3 valence without generating additional harmful defects. More important, the generation of deep energy level defects and defect clusters associated with Sn were suppressed by replacing Sn with Al. Finally, the photovoltaic performance of different Al doped CZTSSe cells were characterized by conducting J-V and external quantum efficiency (EQE) tests. Remarkably, the CZTSSe solar cell with PCE as high as 10.59 % is obtained under a doping level of 6 % Al, which has an open circuit voltage of 522 mv. Compared with reference CZTSSe solar cells with an efficiency of 7.29 %, which indicates with improvement of 45 % in efficiency. Consequently, Al doping process is considered as a prospective tactic to elevate the PCE of CZTSSe solar cells.

Influence of Stacking Order on the Structural and Optical Properties of Cu2ZnSnS4 Absorber Layer Prepared from DC-Sputtered Oxygenated Precursors

Several studies have attempted to overcome the sudden volume expansion of the precursor during sulfurization by the use of oxygen-containing precursors when growing the CZTS absorber. This work demonstrates the influence of precursor stacking orders on the properties of the CZTS thin film absorber layer from DC-sputtered oxygenated precursors for solar cell applications. CZTS absorber layers were prepared from three types of DC-sputtered stacks, namely, Zn-O/Sn/Cu, Sn/Zn-O/Cu, and Sn/Cu/Zn-O. The precursors were sequentially deposited on a soda lime glass (SLG) using DC-magnetron sputtering and annealed in a sulfur and nitrogen ambient. X-ray diffractometry (XRD) and Raman spectroscopy analyses reveal the formation of crystalline kesterite CZTS structure regardless of the precursor stacking order. Atomic force microscope (AFM) analysis showed that CZTS thin films grown from precursor stacks SLG/Zn-O/Sn/Cu and SLG/Sn/Zn-O/Cu had improved morphological properties with densely packed large grains compared to that with stack SLG/Sn/Cu/Zn-O. SLG/Zn-O/Sn/Cu is the best stack among the studied stacking orders since it exhibits large grains in the absorber layer, which is preferential for high-efficiency thin film solar cells. The use of oxygenated precursor with order Sn/Zn-O/Cu promises improved CZTS absorber properties as it exhibits better morphological properties.

Numerical investigation of CuSbS2 thin film solar cell using SCAPS-1D: enhancement of efficiency on experimental films by defect studies

The study of photovoltaic solar cells has been an exciting field of research because of their environmentally friendly nature. Scientists are continuously searching for new methods to develop solar cells that are highly efficient and cost-effective. One promising option is the use of Copper Antimony Sulphide (CuSbS2) based ternary compound semiconductor in ultrathin film photovoltaic cells. This material has a high absorption coefficient, low cost, and is readily available in the earth’s crust. These characteristics make it an ideal candidate for use as a thin-film absorber layer in solar cells. In this work, FTO/CdS/In2S3/CuSbS2/Spiro-OMeTAD/Au device is proposed to improve the efficiency of experimentally designed CuSbS2-based thin film solar cells using numerical modeling. Device simulation was carried out using SCAPS-1D software, and the illumination spectrum used for this optimization was 1.5 AM. The simulated results from SCAPS-1D were compared to the experimental data. After optimizing the device parameters all the electrical parameters of the solar cell were improved. The optimized CuSbS2-based device shows power conversion efficiency (PCE) of 21.11% with short circuit current density (Jsc) of 20.96 mA cm−2, open circuit voltage (Voc) of 1.23 V, and fill factor (FF) of 81.84%. Based on the simulation results, it is possible to increase the performance of the device by varying different parameters such as the defect density of each layer, interfacial defect density, thickness, and doping concentration.

Preparation of nanostructured cuprous oxide (Cu2O) absorber layer for photovoltaic application

AbstractIn this investigation, a nanostructured Cu2O thin film absorber layer is electrodeposited, exploring the impact of varying negative applied voltages and deposition time. Notably, the Cu2O thin film demonstrated optimal absorbance at −0.95 V, contrasting sharply with a minimum at −0.97 V. The authors' findings underscore that the peak absorbance was achieved at −0.95 V, coinciding with the lowest transmittance observed after 80 min of deposition, aligning with a maximal absorption coefficient of 21 × 103 cm−1. At a deposition time of 5 min, the Cu2O thin film exhibited a noteworthy maximum Urbach energy of 2.00 eV and a minimum steepness parameter of 0.013. In contrast, the lowest Urbach energy was recorded at 0.34 eV, with the highest steepness parameter occurring at an applied voltage of 0.93 V. Furthermore, this study revealed a gradual increase in the refractive index with higher applied voltages, reaching its pinnacle at −1.5 V. These results collectively emphasize the nuanced interplay between applied voltage, deposition time and the optical properties of the nanostructured Cu2O thin film. The observed trends hold significant implications for optimizing the performance of thin film absorber layers, particularly in the context of enhancing absorbance and tailoring optical characteristics for specific applications.

A Review on the Fundamental Properties of Sb2Se3-Based Thin Film Solar Cells

There has been a recent surge in interest toward thin film-based solar cells, specifically new absorber materials composed by Earth-abundant and non-toxic elements. Among these materials, antimony selenide (Sb2Se3) is a good candidate due to its peculiar properties, such as an appropriate bandgap that promises a theoretical maximum power conversion efficiency of 33% and an absorption coefficient of around 105 cm−1, enabling its use as a thin film absorber layer. However, charge carrier transport has been revealed to be problematic due to its cumbersome structure and the lack of a doping strategy. In this work, we aim to provide a clear picture of the state-of-the-art regarding research on Sb2Se3-based solar cells and its prospects, from the successful achievements to the challenges that are still to be overcome. We also report on the key parameters of antimony selenide with a close focus on the different characteristics associated with films grown from different techniques.

A Novel Approach for Designing a Sub-Bandgap in CuGa(S,Te)2 Thin Films Assisted with Numerical Simulation of Solar Cell Devices for Photovoltaic Application.

As a well-explored chalcopyrite material, copper gallium sulfide CGS has been considered a potential material for solar cell absorber layers. However, its photovoltaic attributes still require to be improved. In this research, a novel chalcopyrite material, copper gallium sulfide telluride CGST, has been deposited and verified as a thin film absorber layer to fabricate high-efficiency solar cells by experimental testing and numerical simulations. The results display the intermediate band formation in CGST with incorporation of Fe ions. Electrical studies showed enhancement in mobility from 1.181 to 1.473 cm2 V-1 s-1 and conductivity from 2.182 to 5.952 S cm-1 for pure and 0.08 Fe-substituted thin films. The I-V curves display the photoresponse and ohmic nature of the deposited thin films, and the maximum photoresponsivity (0.109 A W-1) was observed for 0.08 Fe-substituted films. Theoretical simulation of the prepared solar cells was carried out using SCAPS-1D software, and the obtained efficiency displayed an increasing trend from 6.14 to 11.07% as the Fe concentration increased from 0.0 to 0.08. This variation in efficiency is attributed to the decrease in bandgap (2.51-1.94 eV) and the formation of an intermediate band in CGST with Fe substitution, which is evidenced in UV-vis spectroscopy. The above revealed results open the way to 0.08 Fe-substituted CGST as a promising candidate as a thin film absorber layer in solar photovoltaic technology.

A simple method for Ge incorporation to enhance performance of low temperature and non-vacuum based CZTSSe solar cells

Despite the slow efficiency development, Cu2ZnSn(S,Se)4 still is a promising absorber material for solar cells for its easy and low cost way of fabrication and the abundance of its elements. Similarly, also CdTe faced a long period when the record efficiency would not improve over 16.5% until a different paradigm was introduced. CZTSSe, compared to other absorbers, has the advantage that can be successfully made by solution-based growth techniques which are unique for their low cost. However this is meaningful only if selenization process is not done at high temperatures and without complicated processes. So we have optimized an easy, low cost, non-vacuum fabrication process for Cu2(Zn,Sn)(S,Se)4 thin-film absorber layers by spin coating of precursor and subsequent lower temperature selenization. A precursor solution is deposited on a Mo coated glass and the stack is then annealed below 450 °C in Se atmosphere and without the application of toxic hydrazine. With this process, we have already presented efficiencies of around 5.5%, but in this work, we introduce a simple impurity inclusion process by treating the surface of the precursor film with chlorine-based compound containing either Na, K or Ge. This allows to improve the open circuit voltage and the current density, with an increase in efficiency of 25% compared to the non-treated sample. The structural modifications are addressed by X-ray diffraction, Raman spectroscopy, atomic force microscopy and scanning electron microscopy. Current-voltage, capacitance-voltage and drive level capacitance profiling are used to analyse performance and defect density in the finished devices.

Growth of Cu2ZnSnS4 thin film absorber layer on transparent conductive oxides and molybdenum substrates by electrodeposition for photovoltaic application

Cu2ZnSnS4 (CZTS) absorber layer for the photovoltaic application was successfully deposited on different substrates, indium tin oxide (ITO), fluorine-doped tin oxide (FTO) and molybdenum (Mo) using a single step electrodeposition process. The structural, morphological and optical properties of the CZTS films were analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and photoluminescence (PL). The present study was designed to determine the effect of the substrate on the kesterite thin film properties grown by electrodeposition. The results confirm that the CZTS properties depend on the substrate nature. Furthermore, the CZTS films deposited on Mo substrate was found more appropriate for CZTS based solar cells due to their crystallinity and good morphology as well as their suitable energy bandgap around 1.6 eV.

Solution-processed CIGS thin film solar cell by controlled selenization process

Cu(In,Ga)Se2 (CIGS) is a prevalent material with superior thermo-chemical stability and excellent optoelectronic properties for solar cell applications. In thin film form, CIGS could be a potentially economicalandbuilding integrated photovoltaicadaptable substitute to Silicon solar cells, solving humanity's extensive energy demands. To be economically sustainable, CIGS thin film processing must be abridged and affordable. We explored a low-cost, simplified wet chemical nano-ink method to make the CIGS thin film absorber layer comprising precursor thin film preparation by spraying CIGS nano-ink and subsequent post-treatment using Selenium vapor under Nitrogen atmosphere at a temperature of 550 °C. The spray-casted nanocrystalline layers were selenized at a low pressure of 1 Torr or 1 atm Nitrogen utilizing elemental pallets of Selenium as a source of Se vapor. The impact of Selenization pressure on the structure, morphology, composition, and electronic conductivity of selenized CIGS thin films absorber is investigated in this study, as well as the device performance associated with the processing parameters.

Modeling of Photovoltaic Solar Cell Based on CuSbS₂ Absorber for the Enhancement of Performance

Research on photovoltaic solar cells has always been exciting due to its clean and green nature. However, the quest for alternative approaches to the design of highly efficient solar cells with optimal cost-efficiency ratios has also been progressing. CuSbS2-based ternary compound semiconductor is a promising candidate for the ultrathin film photovoltaic cell due to the high absorption coefficient, low cost, and earth abundant which makes it suitable to use as a thin-film absorber layer. The impact of various parameters such as thickness, bandgap, band alignment, temperature, carrier concentration, and bandgap grading has been studied to optimize the overall performance of the solar device. In present work, we have adopted the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D) simulation approach to the design of CuSbS2 absorber-based solar heterostructure cells to boost the electrical properties of the solar cell.

Surface texturing of Cu2ZnSnSe4 thin films for enhanced optical absorbance

Thin-film solar absorber layer presenting its surface with periodically patterned structures or with random roughness are considered one of the ways to increase the incident light absorption and thereby enhance the performance of the solar cell. This surface modification in the absorber layer reduces the reflection loss and leads to multiple reflections of the photons that fall on the absorber layer, leading to improved absorbance. In this present work, optical lithography process has been adapted to achieve periodic micro patterning of Cu2ZnSnSe4(CZTSe) solar absorber thin film surface and the changes in optical absorbance is studied. Optimization of the lithography process is undertaken to upscale the area of patterning up to (~20 mm × 20 mm) in CZTSe absorber thin films. CZTSe films were grown using e-beam evaporation and surface patterning is integrated through lithography process. Patterning integrity was examined through optical and scanning electron microscopes. Phase integrity was studied using XRD and Raman spectroscopy tools. The optical absorbance of the flat and patterned CZTSe thin films are measured using UV–Vis-NIR spectrophotometer.

Synthesis and characterization of CdTe thin film on FTO by electrodeposition technique for CdTe/CdS solar cells

In this work, the synthesis of the CdTe thin film (absorber layer) on fluorine-doped Tin oxide (FTO) substrate by electrodeposition technique of CdTe/CdS solar cell has been presented. As a result of the superior efficiency in energy conversion by absorbing energy in a broad range of the solar spectrum, thin film CdS/CdTe solar cells have been paid attention worldwide as a potential candidate for photovoltaics (PV). The electrodeposition (ED) technique is suitable for the synthesis of CdTe material due to its ease, low cost, scalability and manufacturability. Usually, the quality of these deposited thin films depends on several growth parameters, and the type of conducting glass substrate plays a crucial role. CdTe material grown up on the top of the FTO coated glass substrate having dimensions 75mm* 25mm*1mm and was characterized for its optical properties by UV-Vis spectrometer (UV-Vis), Photoluminescence (PL) and Fourier transform infrared spectrometer (FTIR). XRD result confirms the cubic crystalline character of the deposited material. The band gap of CdTe film estimated using Tauc’s plot is found to be 1.5eV. It is expected that this article will enrich the features of CdTe/CdS devices for solar energy conversion and stimulate further innovative research interest on this interesting topic.

Strain Mapping of CdTe Grains in Photovoltaic Devices

Strain within grains and at grain boundaries (GBs) in polycrystalline thin-film absorber layers limits the overall performance because of higher defect concentrations and band fluctuations. However, the nanoscale strain distribution in operational devices is not easily accessible using standard methods. X-ray nanodiffraction offers the unique possibility to evaluate the strain or lattice spacing at nanoscale resolution. Furthermore, the combination of nanodiffraction with additional techniques in the framework of multimodal scanning X-ray microscopy enables the direct correlation of the strain with material and device parameters such as the elemental distribution or local performance. This approach is applied for the investigation of the strain distribution in CdTe grains in fully operational photovoltaic solar cells. It is found that the lattice spacing in the (111) direction remains fairly constant in the grain cores but systematically decreases at the GBs. The lower strain at GBs is accompanied by an increase of the total tilt. These observations are both compatible with the inhomogeneous incorporation of smaller atoms into the lattice, and local stress induced by neighboring grains.

Influence of deposition time in CdTe thin film properties grown by Close-Spaced Sublimation (CSS) for photovoltaic application

Abstract Cadmium Telluride (CdTe) thin films were grown on borosilicate glass substrates by close-spaced sublimation (CSS) at a pressure of 1.5–2 Torr in Ar ambient. CdTe thin films were sublimed at a source temperature of 625 °C and substrate temperature of 595 °C. In this study, the impact of various deposition times on the structural, morphological, topographical, electrical and optical properties of CdTe thin films has been explored to achieve high quality thin film absorber layer for solar cells applications. The crystalline structure, surface morphology, surface topology, electrical and optical properties of the films were examined by using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), Hall Effect measurement and UV–Vis spectrophotometry, respectively. XRD investigation demonstrated that CdTe film shows polycrystalline nature pronounced with cubic zinc blende structure with a strong preferential (1 1 1) orientation. The FESEM images illustrated that the surface morphology and the average grain size of the films were dependent on the deposition times of CdTe thin films. AFM analysis revealed noteworthy changes in the film’s surface roughness values for different deposition times. Carrier concentration was found in the order of 1013 cm−3. Band gap of CdTe thin film was found in the range 1.45–1.48 eV, which is suitable to be used in CdTe thin film solar cells.

Various Metal Sandwich Layer Oriented Efficiency Enhancement Superiority on CuInGaSe2 Thin Film Solar Cells

The good quality CuInGaSe2 (CIGS) thin film solar cells were fabricated on molybdenum metal coated soda lime glass substrate. Three-stage co-evaporation method was utilized for the fabrication of high quality p-type CIGS thin film absorber layer. Further, n-type CdS layer, high resistive intrinsic ZnO layer and transparent conducting AlZnO layers were fabricated by CBD method and vacuum sputtering methods. We made three various top metal sandwich grid patterns, i.e. Al, Al/Cu and Cu/Al which were utilized to investigate the metal sandwich layer oriented efficiency enhancement superiority on CuInGaSe2 thin film solar cells. The investigated specific CIGS solar cell device efficiency with respect to various top metal grid sandwich patterns is presented and discussed.

Synthesis and Characterization of Copper-Zinc-Tin-Sulfide (CZTS) Thin Film Absorber Layer for Solar Cell Application

Synthesis and Characterization of Copper-Zinc-Tin-Sulfide (CZTS) Thin Film Absorber Layer for Solar Cell Application

Cu(In,Ga)Se2 thin film absorber layer by flash light post-treatment

Cu(In,Ga)Se2 (CIGS) thin film solar cell has immerged popular candidate as a cost-effective alternative for conventional silicon-based solar cells owing to its excellent optoelectronic properties and better thermo-chemical stability. Non-vacuum process for the preparation of CIGS absorber is always preferred for its economical benefits over the vacuum based process. In this regard, we present solution processed development of CIGS absorber layer involving pristine thin film by spray casting of nanoparticulate ink followed by photonic flash light sintering post-treatment. Influence of flash light post-treatment on structural, morphological, optical and photovoltaic properties of CIGS thin film absorber layer is presented.

Electrodeposition of near stoichiometric CuInSe2 thin films for photovoltaic applications

This work investigates on the single step electrodeposition of quality CuInSe2 (CIS) thin film absorber layer for photovoltaics applications. The electrodeposition was carried using an aqueous acidic solution with a pH of 2.25. The deposition was carried using a three electrode system in potentiostatic conditions for 50 minutes. The as-deposited and nitrogen (N2) annealed films were characterized using XRD, FE-SEM and Raman spectroscopy. It has been observed that the SDS has the tendency to suppress the copper selenide (CuxSe) secondary phase which is detrimental to the device performance.

Optimization of Cu2ZnSnS4 thin film absorber layer growth without sulphurization using triethanolamine as complexing agent for thin film solar cells applications

Quaternary kesterite Cu2ZnSnS4 (CZTS) thin films have been prepared via a simple spin-coating technique based on a sol–gel precursor of 2-methoxyethanol solution with metal salts and thiourea. Solution processed CZTS thin film growth parameters using complexing agent triethanolamine (TEA) have been investigated. Effects of complexing agent TEA on structural, morphological, optical, electrical and photovoltaic properties of CZTS thin films were systematically investigated. X-ray diffraction and Raman spectroscopy studies reveal that amorphous nature of CZTS thin film changes into polycrystalline with kesterite crystal structure with optimized TEA concentartion. Surface morphology of CZTS films were analyzed by field emission scanning electron microscope and atomic force microscope, which revealed the smooth, uniform, homogeneous and densely packed grains and systematic grain growth formation with varying TEA concentrations. UV–Vis spectra revealed a direct energy band gap ranging from 1.78 to 1.50 eV, which was found to depend upon the TEA concentration. X-ray photoelectron spectroscopy demonstrated stoichiometric atomic ratios of multicationic quaternary CZTS thin film grown without sulphurization. p-type conductivity was confirmed using Hall measurements and the effect of varying concentartion of TEA on electrical and photovoltaic properties are studied. The SLG/FTO/ZnO/CZTS/Al thin film solar cell is fabricated with the CZTS absorber layer grown at optimized TAE concentration of 0.06 M. It shows a power conversion efficiency of 0.87% for a 0.16 cm2 area with Voc = 0.257 mV, Jsc = 8.95 mA/cm2 and FF = 38%.