Thin Film Photovoltaic Solar Cells Research Articles

Growth and Characterization of p-Type and n-Type Sb2Se3 for Use in Thin-Film Photovoltaic Solar Cell Devices

In this study, a two-electrode electrodeposition technique was employed to grow thin films of antimony selenide (Sb2Se3) on glass/fluorine-doped tin oxide (FTO) substrates. The highest quality thin films were consistently obtained within the range of 1600 mV to 1950 mV. Subsequent electrodeposition experiments were conducted at discrete voltages to produce various layers of thin films. Photoelectrochemical cell (PEC) measurements were performed to characterize the semiconductor material layers, leading to the identification of both p-Type and n-Type conductivity types. Optical absorption spectroscopic analysis revealed energy bandgap values ranging from 1.10 eV to 1.90 eV for AD-deposited Sb2Se3 samples and 1.08 eV to 1.68 eV for heat-treated Sb2Se3 samples, confirming the semiconducting nature of the Sb2Se3 material. Additionally, other characterization techniques, including X-ray diffraction analysis, reveal that the AD-deposited layers are almost amorphous, and heat treatment shows that the material is within the orthorhombic crystalline system. Heat-treated layers grown at ~1740 mV showed highly crystalline material with a bandgap nearing the bulk bandgap of Sb2Se3. Raman spectroscopy identified vibrational modes specific to the Sb2Se3 phase, further confirming its crystallinity. To explore the thin-film morphology, Scanning Electron Microscopy (SEM) was employed, revealing uniformly deposited material composed of grains of varying sizes at different voltages. Energy Dispersive X-ray analysis (EDX) confirmed the presence of antimony and selenium in the material layers.

An ITO-Free Kesterite Solar Cell.

Photovoltaic thin film solar cells based on kesterite Cu2 ZnSn(S, Se)4 (CZTSSe) have reached 13.8% sunlight-to-electricity conversion efficiency. However, this efficiency is still far from the Shockley-Queisser radiative limit and is hindered by the significant deficit in open circuit voltage (VOC ). The presence of high-density interface states between the absorber layer and buffer or window layer leads to the recombination of photogenerated carriers, thereby reducing effective carrier collection. To tackle this issue, a new window structure ZnO/AgNW/ZnO/AgNW (ZAZA) comprising layers of ZnO and silver nanowires (AgNWs) is proposed. This structure offers a simple and low-damage processing method, resulting in improved optoelectronic properties and junction quality. The ZAZA-based devices exhibit enhanced VOC due to the higher built-in voltage (Vbi ) and reduced interface recombination compared to the usual indium tin oxide (ITO) based structures. Additionally, improved carrier collection is demonstrated as a result of the shortened collection paths and the more uniform carrier lifetime distribution. These advances enable the fabrication of the first ITO-free CZTSSe solar cells with over 10% efficiency without an anti-reflectivecoating.

Scrutinizing the effect of substrate temperature and enhancing the multifunctional attributes of spray deposited copper gallium sulfide (CuGaS2) thin films

ABSTRACT Polycrystalline chalcopyrite CuGaS2 thin films were prepared using a spray pyrolysis route has been considered a potential material for the solar cell absorber layer. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) studied the impact of substrate temperature in the range of 200–300˚C on surface profile and roughness. Powder X-ray diffraction disclosed that the films were polycrystalline at all examined substrate temperatures, with crystallite size increasing with increased substrate temperature. The UV-Vis displays the cut-off wavelength in 550–880 nm for varied substrate temperatures of CuGaS2 thin films, and the observed band gap is 2.75 eV–1.89 eV. The electrical attributes showed the enhancement in mobility (4.632 cm2 V−1 s−1) for varied substrate temperatures of CuGaS2 thin films. The 300˚C temperature sprayed CuGaS2 polycrystalline films are a decent candidate to be apposite as an absorber layer in thin film photovoltaic solar cells.

Simulation and Numerical Investigation of the Effect of Temperature and Defect on ZnTe/ZnSe/ZnO Thin-Film Photovoltaic Solar Cell Performance Efficiency

Thin film-based solar cell semiconductor emerges as a promising candidate for solar photovoltaic future applications. A proposed heterojunction ZnTe/ZnSe/ZnO thin film-based solar cell has been simulated by using Solar Cell Capacitance Simulator-One Dimension (SCAPS-1D) in order to study the impact of temperature and defect layers on its efficiency parameters. The heterojunction thin film-based solar cell has been selected for simulation due to its low cost, availability, and reduced toxicity compared to other absorber layer materials. Numerical modeling has been used to comprehend device properties before fabrication. The results indicate that the efficiency parameters (Jsc, VOC, FF, and η) have been significantly affected by temperature and the presence of defect layers. The simulated J-V characteristics demonstrate how defect density affects solar cell efficiency parameters. In the defect system, the efficacy parameters have been reduced except for a slight increase in VOC at 300 K. The findings of this study are significant as they demonstrate the importance of understanding the impact of temperature and defect layers on the performance of thin film-based solar cells. The use of numerical modeling tools like SCAPS-1D can aid in the design and development of new solar cell technologies, which could ultimately lead to the widespread adoption of solar energy as a clean and sustainable energy source.

Enhanced Performance of Ternary CuGaSe 2 Thin‐Film Photovoltaic Solar Cells and Photoelectrochemical Water Splitting Hydrogen Evolution with Modified p–n Heterointerfaces (Adv. Mater. Interfaces 25/2022)

Efficient Photovoltaic Solar Cell and Hydrogen Evolution Using CuGaSe2-based Photoabsorber Layers In article number 2201266, Shogo Ishizuka, Riku Okamoto, Shigeru Ikeda, and co-workers develop an interface modification technique using Cu-deficient phases, alkali-metal doping, and an n-type buffer material for enhancing performance of CuGaSe2 thin-film photovoltaic solar cells and photoelectrochemical water splitting hydrogen evolution.

Significant improvement of conversion efficiency by passivation of low-angle grain boundaries in flexible low-cost single-crystal-like GaAs thin-film solar cells directly deposited on metal tape

We develop an easily implementable yet effective process to achieve high power conversion efficiency in newly-developed flexible single-crystal-like GaAs thin-film photovoltaic solar cells on cheap metal tape. We study various techniques on the fabricated devices to passivate the defect states associated with dangling bonds at low-angle grain boundaries (LA-GBs) existing in the single-crystal-like GaAs material. We report that sulfur by trioctylphosphine sulfide (TOP:S) solution treatment can partially but effectively passivate the defect states at the LA-GBs to increase all the solar cell performance parameters of open-circuit voltage VOC (33.2%), short-circuit current JSC (19.5%), and fill factor FF (25.8%), resulting in the improvement of the power conversion efficiency more than double. The material and device characterizations and numerical modeling are performed to propose a mechanism, also suggesting that the power conversion efficiency higher than 20%, which is an important target milestone in emerging solar cell technologies, can be achieved. This work presents the first effective passivation of the bulk defects in GaAs at the device level and can also offer a solution for other photonic and electronic devices using non-single-crystalline GaAs films for flexible electronics.

Design of a Highly Efficient Subwavelength Antireflective Structure for Solar Cells

An efficient optical antireflective (AR) structure plays a vital role in high-performance thin-film solar cells. Here, we design a surface relief AR structure consisting of a two-dimensional (2D) array of a subwavelength ring and pillar-shaped feature, capable of suppressing optical reflection over a wide spectral window of the solar spectrum. Our simulations show that the weighted average reflectance of the subwavelength AR structure is as low as 4.2% in the 400–1100 nm spectral range in the normal incidence condition and almost 10-fold reduction compared with a bare silicon surface. When placed on the front side of a simple Si thin-film photovoltaic solar cell, this subwavelength AR structure leads to an improved light absorption with simulated results showing an increase of 53% short-circuit current compared to a flat solar cell. Besides, our simulations show that this AR structure could, in principle, perform well against reasonable fabrication errors.

Physical and chemical aspects at the interface and in the bulk of CuInSe2-based thin-film photovoltaics.

Chalcopyrite CuInSe2 (CISe)-based thin-film photovoltaic solar cells have been attracting attention since the 1970s. The technologies of CISe-based thin-film growth and device fabrication processes have already been put into practical applications and today commercial products are available. Nevertheless, there are numerous poorly understood areas in the physical and chemical aspects of the underlying materials science and interfacial and bulk defect physics in CISe-based thin-films and devices for further developments. In this paper, current issues in physical and chemical studies of CISe-based materials and devices are reviewed. Correlations between Cu-deficient phases and the effects of alkali-metals, applications to lightweight and flexible solar minimodules, single-crystalline epitaxial Cu(In,Ga)Se2 films and devices, differences between Cu(In,Ga)Se2 and Ag(In,Ga)Se2 materials, wide-gap CuGaSe2 films and devices, all-dry processed CISe-based solar cells with high photovoltaic efficiencies, and also fundamental studies on open circuit voltage loss analysis and the energy band structure at the interface are among the main areas of discussion in this review.

Numerical Modeling of High Conversion Efficiency FTO/ZnO/CdS/CZTS/MO Thin Film-Based Solar Cells: Using SCAPS-1D Software

The numerical modeling of a copper zinc tin sulfide (CZTS)-based kesterite solar cell is described in detail in this article. To model FTO/ZnO/CdS/CZTS/MO structured solar cells, the Solar Cell Capacitance Simulator-one-dimension (SCAPS-1D) program was utilized. Numerical modeling was used to estimate and assess the parameters of various photovoltaic thin film solar cells. The impact of different parameters on solar cell performance and conversion efficiency were explored. Because the response of a solar cell is partly determined by its internal physical mechanism, J-V characteristic characteristics are insufficient to define a device’s behavior. Regardless of the conviction in solar cell modeling, variable attributes as well as many probable conditions must be handled for simulation. Promising optimized results were obtained with a conversion efficiency of (η% = 25.72%), a fill factor of (FF% = 83.75%), a short-circuit current of (JSC = 32.96436 mA/cm2), and an open-circuit voltage of (VOC = 0.64 V). The findings will aid in determining the feasibility of manufacturing high-efficiency CZTS-based solar cells. First, in the SCAPS-1D environment, the impacts of experimentally constructed CZTS solar cells were simulated. The experimental data was then compared to the simulated results from SCAPS-1D. After optimizing cell parameters, the conversion efficiency of the improved system was observed to rise. The influence of system factors, such as the thickness, acceptor, and donor carrier concentration densities of the absorber and electron transport layers, and the effect of temperature on the efficiency of CZTS-based photovoltaic cells, was explored using one-dimensional SCAPS-1D software. The suggested findings will be extremely useful to engineers and researchers in determining the best method for maximizing solar cell efficiency, as well as in the development of more efficient CZTS-based solar cells.

Electrodeposition in Ionic Liquids for Controlled Synthesis of New Class of Ionic Semiconductors Based on Binary and Ternary Chalcogenide Perovskites for Thin Film Photovoltaic Solar Cells

Thin film photovoltaic (PV) solar cells based on Cu(In,Ga)(S,Se)2 (CIGS), CdTe and Cu2ZnSnS4 (CZTS) have been in the forefront of the pursuit for sustainable and pervasive solar electricity utilization. Recently, researchers have focused on alternative semiconductor photo-absorbers that can be synthesized as thin films by simple low cost solution based methods. Efforts in this direction led to solar cells based on the hybrid organic-inorganic perovskite photo-absorbers having the general formula RNH3MX3 where R= CnH2n+1, M= Pb, Sn and X= Cl, I or Br showing significantly high (24.2%) conversion efficiency. However, the light induced instability, mechanical durability and thermal degradation problems though largely elucidated, still require intensive efforts towards alleviation. The key factors for high efficiency of hybrid perovskite cell are high absorption coefficient, defect-tolerance and large carrier diffusion lengths. This is attributed to their ionic character derived from higher cation-anion coordination resulting in enhanced Coulomb interaction. The entirely inorganic chalcogenide perovskites are the ionic semiconductor counterparts which are purported to have similar optoelectronic properties sans the stability issues but have not been investigated in detail. The perovskite ionic semiconductors with formula unit ABX3 (A=Ca, Ba or Sr ; B=Ti or Zr; X= S, Se) have direct 0.8-2.4 eV bandgap, high photo-absorption and large carrier mobility. These appear attractive for photovoltaic solar cell application but are needed to be investigated as thin films by emphasizing the synthesis-property correlations. In this work we have investigated electrodeposition synthesis in ionic liquid medium of the transition metal layered chalcogenide TiS2 and p-type CaTiS3 perovskite chalcogenide semiconductor thin films which have application in solar cells, the former as a hole conductor and the later as an efficient photo-absorber.In this work we describe an ab initio study of scalable electrodeposition of TiS2 and CaTiS3 polycrystalline semiconductor thin films from choline chloride–urea eutectic based ionic liquid electrolytes at 80°C and establish their structure and optoelectronic properties dependent upon the electrodeposition variables. The ionic liquid electrodeposition, not studied in detailed for semiconductor layers, is unique due to large stable potential window, high solubility for metal salts and devoid of hydrogen interference usual in aqueous medium. Further, it enables electrodeposition of semiconductor with elements having high reduction potential like Ca and Ti. We synthesized these films by electrodeposition in a 3-cell assembly with Pt reference and counter electrode and transparent conducting glass (FTO) as substrate. Precursors TiCl4, CaCl2 and Na2S2O3 served as source of Ti, Ca and S and initial cyclic voltammetry (CV) studies with variable precursor composition have established deposition potentials of Ca and Ti as -0.68V and -0.79V vs Pt, respectively.Detailed CV study with variable Ca:Ti precursor ratio coupled with film composition analysis establishes deposition potential and precursor composition for stoichiometric CaTiS3 film synthesis. X-ray diffraction showed as-electrodeposited films are polycrystalline. The Raman spectra includes numerous peaks in the 50-1200 cm-1 range which are interpreted as characteristic vibration modes of CaS at 170 and 220 cm-1. The variation in the intensity of the A1g mode at 359 cm-1 originating from TiS2 was used to calibrate the deposition potential relative to film composition. Tauc analysis of the uv-vis transmission spectra showed direct bandgap of 1.5 eV which is ideal for terrestrial solar radiation absorption. A correlation of the electrochemical deposition potential with the inclusion of secondary phases was noticed. This also resulted in the increase in the bandgap energy indicating possibility for adjusting bandgap for specific solar cell structures. The TiS2 layered chalcogenide with potential use as hole transport layer in chalcogenide perovskites was likewise electrodeposited. Detailed analysis of the reduction peaks in CV plots shows peak at -0.76V vs Pt corresponding to TiS2 formation and a rapidly rising current wave corresponds to under potential deposition. The direct electrodeposition of TiS2 is by reduction of Ti at substrate and instant sulfurization in presence of S2- ions. The granular growth is directed by FTO which provides electrochemical reduction and nucleation sites for TiS2 polycrystalline film growth as established by X-ray diffraction. All Raman peaks are interpreted belonging to TiS2 and partial phase mixing with the TiS3 depending on the electrodeposition potential was seen. Thus, the observed decrease in the bandgap with increase in potential can be used for integrating TiS2 in solar cells as hole conductor as well as an absorber depending on the configuration, This paper will report on the detailed effect of the variables used in ionic liquid electrodeposition and consequent structural and optoelectronic properties of the two important ionic semiconductors for assessment of their use in solar cells.

Growth and optical properties of nanocrystalline Sb2Se3 thin-films for the application in solar-cells

Antimony selenide (Sb2Se3) is a promising material for thin-film solar-cells due to its attractive optoelectronic properties with the desirable band gap. In the present work, four different Sb2Se3 films were grown on Si/SiO2 (100) substrates at ambient temperature using ultra-high vacuum molecular beam evaporation technique and different evaporation temperatures. The compositional analysis with the help of wavelength-dispersive X-ray spectroscopy measurements demonstrate that there is a loss of Se in the as-deposited samples. However, the X-ray diffraction study indicates that the as-deposited films are nanocrystalline in nature, with average crystallite size slightly increasing with the evaporation temperature. The blue shift of Raman peaks with the increase of evaporation temperature indicates the possibility of the presence of small amount of compressive strain in the crystal lattice and it appears because of the anion vacancy (VSe) due to the loss of Se. The obtained band gap value ranges from 1.075 eV to 1.21 eV, which indicate that the as-deposited nanocrystalline Sb2Se3 films are suitable for application in thin-film photovoltaic solar-cells. The tuning of the band-gap with the evaporation temperature opens a new road to optimize the device efficiency for the low-cost thin-film photovoltaics.

Novel chemical approach to synthesis and characterization of greener and rock-like Cu2ZnSnS3Se (CZTSSe) thin films of kasterite structure

Abstract The growing requirement to enlarge cost-effective sustainable renewable energy technologies for future generations of solar cells due to reservoirs of fossil fuels are being run out in near future. Their excessive use has created serious environment issues like global warming, pollution etc. Considering about photovoltaic thin film solar cells, Cu2ZnSnS3Se (CZTSSe) are particularly interesting because of their high absorption coefficients greater than 104 cm−1, good photostability and confirmed high photovoltaic efficiency. Their direct tunable band gaps as well as their constituent elements are highly plentiful in earth’s crust, non-toxic and cheaply available in market which give greener and cost effective way to synthesize thin film solar cells. Taking this positive approach we have tried to focus synthesis of Cu2ZnSnS3Se (CZTSSe) thin films by appropriate, inexpensive chemical bath deposition technique. The films obtained were uniform and high quality in appearance. The films were characterized by X-Ray diffraction, Raman, Scanning Electron Microscope, EDS, UV–Visible Spectrophotometer, electrical conductivity and PEC studies. The band gap obtained from the transmission spectra which is tunable for solar absorption. The outstanding thing is that synthesis of CZTSSe thin films were carried out at low temperature. The result of XRD and Raman confirms Pure Kasterite phase and formation of CZTS3Se. The SEM gives typical rock like morphology and EDS confirms fair stoichiometry while band gap was estimated upto 1.32 eV which also supported by strongly by PL spectroscopy. The conversion efficiency analysed by PEC study up to 1.47%.

Correlation and optimization of the optoelectrical properties of DC magnetron-sputtered Cu2ZnSnS4 absorber layer as a function of the material composition

Sequential DC magnetron sputtering and rapid thermal processing appear very promising to fabricate CZTS-based thin-film photovoltaic (PV) solar cells with regards to existent environmental and industrial issues. However, their state-of-the-art efficiency remains limited to about 10% to date. In this work, we aim at optimizing the optical and electrical properties of the CZTS absorber by an extensive screening of their correlation with the material composition. This is widely varied by different deposition (i.e. thickness of precursors) and process (i.e. RTP) conditions. We assess the impact of absorber composition on the energy bandgap, absorption coefficient, p-type carrier concentration and mobility. The most important results lie in the extensive analysis of the inverse power-law trend for carrier concentration versus mobility and logarithmic trend versus bandgap. Our conclusions point the optimal composition ratios towards Cu-poor and less than actual target Zn-rich range. As a result, a potential roadmap is drawn up based on presented experimental results and SCAPS simulations in order to reach more than 10% cell efficiency with the target technology.

Coupled optoelectronic simulation and optimization of thin-film photovoltaic solar cells

A design tool was formulated for optimizing the efficiency of inorganic, thin-film, photovoltaic solar cells. The solar cell can have multiple semiconductor layers in addition to antireflection coatings, passivation layers, and buffer layers. The solar cell is backed by a metallic grating which is periodic along a fixed direction. The rigorous coupled-wave approach is used to calculate the electron-hole-pair generation rate. The hybridizable discontinuous Galerkin method is used to solve the drift-diffusion equations that govern charge-carrier transport in the semiconductor layers. The chief output is the solar-cell efficiency which is maximized using the differential evolution algorithm to determine the optimal dimensions and bandgaps of the semiconductor layers.

Triangle grating for enhancement the efficiency in thin film photovoltaic solar cells

This paper studies the different surface grating shape and their effects on the optical, electrical properties and efficiency of thin film solar cell model. The semiconductor transport model is applied for solving the electrical properties, whereas the optical effect was added using electromagnetic modeling. The efficiency of the model using triangle grating was 12.24% and in the model without grating was 7.75%. The PV efficiency was improved by 4.51% in case of triangle grating. The maximum power observed in triangle grating is 12.5 [mW] that makes difference with [5 mW] than without grating model, and also the current density is 12.5 [mA/cm2]. The absorbance coefficient of the two models enhanced by 20% increase on photon absorbance in the modeled solar cell.

Scalable honeycomb top contact to increase the light absorption and reduce the series resistance of thin film solar cells

This paper presents a novel design for the top contact of thin film photovoltaic (PV) solar cells. The new top contact is formed by fabricating a 20nm thin honeycomb shaped silver mesh on top of an ultra-thin 13nm of indium tin oxide. The new top contact offers the potential to reduce the series resistance of the cell while increasing the light current via plasmonic resonance. Using the nano-bead lithography technique the honeycomb top contact was fabricated and electrically characterized. The experimental results verified the new contact reduces the sheet resistance by about 40%. Numerical simulations were then used to analyze the potential performance enhancement in the cell. The results suggest the proposed top contact integrated with a typical thin film hydrogenated amorphous silicon PV device would lead to more than an 8% improvement in the overall efficiency of the cell.

Disordered nanophotonic surfaces for enhanced light collection in semiconductor solar cells

We present a theoretical study of rough photonic surfaces and disordered photonic crystal wire and hole (slab) geometries as a scattering entrance layer to enhance the absorption in thin-film photovoltaic solar cells. One commonly accepted gold standard for scattering enhanced absorption in solar films is given by the Lambertian limit, which results in an optical path length enhancement of 4n2, where n is the refractive index. However, this limit is often an idealized upper limit and hard to realize in practice. Exploiting finite-difference time-domain simulations of realistic rough surfaces, we first explore the limitations and potential practical implementation of this ideal enhancement. A practical rough film, characterized by the RMS height (σRMS) and correlation length (Lx,y) of the random peaks, is numerically optimized for different substrate thicknesses over an optical wavelength range of 400–1100 nm. This optimized surface reflects one practical solution for Lambertian slab thicknesses above 500 nm and wavelengths in the near-UV, but performs worse in the near-IR (∼80%). The physical total height of the optimal rough surfaces is found to be of the order of 2 μm, which contradicts the common assumption that absorption losses within the rough film are negligible. We also investigate photonic crystal wire and slab holes structures with positional and radial disorder, for a fixed height of 1 μm with reflective Ag substrates, considering both GaAs and c-Si semiconductors. We show that the best performing GaAs nanowires give the largest total short-circuit current density (Jsc) of 30  mA/cm2. Relative to the unpatterned slabs of the same height, the greatest photonic crystal enhancements in absorption were seen for c-Si nanoholes and GaAs nanowires (enhancement factors of 1.65 and 1.33, respectively). The inclusion of lattice disorder is shown to increase the absorption enhancement in all photonic crystal structures by 4%–15%, except GaAs nanoholes, which remained within 1% of the ordered structure. Using an analysis of the computed local density of photon states, which is strongly dependent on the complex dielectric constant of the semiconductor, we demonstrate that, due to the higher inherent material losses in GaAs, the useful effects of disorder-induced broadening are minimized in GaAs, compared to c-Si.

Enhanced efficiency of Cu(In,Ga)Se2 solar cells by adding Cu2ZnSn(S,Se)4 absorber layer

A new structure of thin film solar cells, with Cu(In,Ga)Se2 (CIGS) and Cu2ZnSn(S,Se)4 (CZTSSe) as absorber layers, CdS as a buffer layer and ZnO as a window layer, has been simulated using SCAPS one-dimensional simulation program. The aim of the present contribution is to investigate the performance of thin film photovoltaic solar cells. The influences of several factors on the photovoltaic cell parameters are estimated. It is found that by adding CZTSSe as an absorber layer in the conventional CIGS solar cell, the efficiency is enhanced from 17. 91% up to 21.84%, bearing in mind that when only CIGS is used, with the same thickness, we get an efficiency of 19.19%. This result may help in overcoming the problem of the high cost and scarcity of some of the materials, such as indium and gallium used in the production of CIGS solar cells.

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.

PV Absorber Layered Materials Formation Using Potential Pulse Atomic Layer Deposition (PP-ALD),

Thin film photovoltaic solar cells are a promising avenue for solar technology. However, they currently are not as cost effective as fossil fuels. Several absorber layer materials have been formed using various methods in the past. CuIn(1-x)GaxSe2(CIGS) is a promising material due to its tunable direct bandgap, allowing thin films to be used in photovoltaic devices. Previous studies of CIGS done by the author’s group investigated thin film deposition using electrochemical atomic layer deposition (E-ALD). Potential Pulse Atomic Layer Deposition (PP-ALD) is an electrochemical method of atomic layer deposition that relies on alternating cathodic and anodic potential pulses. Cathodic potential pulses long enough to form fractions of a monolayer are used. This is followed by an anodic potential which makes use of the underpotential deposition (UPD) phenomenon to strip away excess bulk, allowing stoichiometric deposits. Because short pulses are used, there is not enough time for excess elemental layers to be formed. PP-ALD is also a one solution co-electrodeposition technique. This differs from the previous E-ALD, which required multiple solution switching, allowing for PP-ALD to have shorter deposition cycles, saving solution and time. Initial results for the formation of In2Se3 and other components of the CIGS compound will be discussed.