Thin Films For Photovoltaic Applications Research Articles

AlZnO magnetron sputtered thin film for photovoltaic application

Aluminum zinc oxide (AZO) is a nontoxic and a low-cost material that finds application as a transparent conducting electrode in photovoltaic devices. In this study the (direct current) DC magnetron sputtering of AZO films is carried out at different deposition times of 5, 10, 15, 20 and 25 min’s at room temperature and it’s structural, optical, electrical and morphological properties are studied for its use as a front contact for thin film solar cell application. The structural study suggests that the preferred orientation of grains along (002) plane having hexagonal structure and the optical and the electrical studies suggest that the films show an average transmission of 70% and a resistivity of the order of 10-4Ωcm. On the other hand, the scanning electron microscopy (SEM) images suggest the formation of packed grains having a homogeneous surface. Moreover in order to study the optoelectronic properties of prepared samples, the electronic and optical calculations of the AZO are performed by the first-principles calculations using density functional theory (DFT).

Solution‐Processed Sb2(S,Se)3 Seed‐Assisted Sb2Se3 Thin Film Growth for High Efficiency Solar Cell

Antimony selenide (Sb2Se3) emerges as a promising sunlight absorber in thin film photovoltaic applications due to its excellent light absorption properties and carrier transport behavior, attributed to the quasi‐one‐dimensional Sb4Se6‐nanoribbon crystal structure. Overcoming the challenge of aligning Sb2Se3‐nanoribbons normal to substrates for efficient photogenerated carrier extraction, a solution‐processed nanocrystalline Sb2(S,Se)3‐seeds are employed on the CdS buffer layer. These seeds facilitate superstrated Sb2Se3 thin film solar cell growth through a close‐space sublimation approach. The Sb2(S,Se)3‐seeds guided the Sb2Se3 absorber growth along a [002]‐preferred crystal orientation, ensuring a smoother interface with the CdS window layer. Remarkably, Sb2(S,Se)3‐seeds improve carrier transport, reduce series resistance, and increase charge recombination resistance, resulting in an enhanced power conversion efficiency of 7.52%. This cost‐effective solution‐processed seeds planting approach holds promise for advancing chalcogenide‐based thin film solar cells in large‐scale manufacturing.

Effect of deposition time on the physicochemical properties of co-electrodeposited Cu2SnS3 thin films for photovoltaic applications

This study highlights our optimization of the co-electrodeposition duration of Cu, Sn, and S on the titanium substrate in order to further improve the properties of Cu2SnS3 thin films in photovoltaic applications. After cyclic voltammetry identifying the potential for simultaneous Cu, Sn and S deposit, "Cu–Sn–S″ layers were electrodeposited for deposition durations ranging from 10 → 20 min. Structurally, X-ray-diffraction and Raman-spectroscopy have confirmed the formation of the single Cu2SnS3-phase, crystallizing in the triclinic system after 20 min of electrodeposition. For this duration, the morphological SEM-EDX profile revealed a highly uniform distribution of grains with very optimal sizes for solar cell applications. To reinforce these conclusions, an optical analysis was carried out in the visible wavelength range, highlighting a strong absorption of the developed sample. In addition, the optical gap estimate, indicates that Cu2SnS3 exihibts a direct transition with a bandgap varying from 1.22 to 1.49eV when the deposition time is increased from 10 →20 min.

A review of recent advances of kesterite thin films based on magnesium, iron and nickel for photovoltaic application: insights into synthesis, characterization and optoelectronic properties

Abstract This review emphasizes the recent advancements and prospects of thin-film kesterite-based photovoltaic (PV) applications using magnesium, iron and nickel. The quest for novel materials employed in solar cells has resulted in incorporating these elements into the composition of kesterite as substitutes or modifiers (dopants) for zinc. This integration has induced notable repercussions on the structural, optoelectronics and morphological properties, which are reviewed. The first section of this paper offers a comprehensive review of the general characteristics of kesterite minerals. These crucial materials exhibit a high absorption coefficient (104 cm–1) and an optical band gap of 1.0–1.8 eV. Moreover, they are free of critical raw materials, non-toxic and sustainable. The second section depicts the substitution or modification of zinc by magnesium in kesterite. Additionally, this paper provides a comprehensive review of the quaternary and pentanary systems Cu2MgSn(S,Se)4 and Cu2Zn1–xMgxSnS4, highlighting their advantages and drawbacks. In the last section, a review of the quaternary or pentanary systems is conducted, namely Cu2ZnxFe1–xSnS4 and Cu2ZnxNi1–xSnS4, along with their effects on optoelectronic properties. In conclusion, various methods for obtaining modified or substituted kesterite materials using magnesium, iron and nickel have demonstrated sustainability, scalability for industrial production and potential candidacy as substitutes for conventional PV materials. The prospects for pentanary materials (Cu2Zn1‑xMgxSnS4, Cu2Zn1‑xFexSnS4 and Cu2Zn1‑xNixSnS4) are to overcome the efficiency record of kesterite reported in 2014, which was 12.6 % for Cu2ZnSn(S,Se)4, and to enhance its optoelectronic properties through synthesis conditions that comply with the principles of green chemistry.

Comparison of polycrystalline and epitaxial Cu(In, Ga)Se2 solar cells with conversion efficiencies of more than 21%

Polycrystalline Cu(In,Ga)Se2 (CIGS) solar cells are widely studied for their application in thin-film photovoltaics, but analysis of their crystalline properties is difficult owing to the presence of grain boundaries and defects. Epitaxial CIGS (epi-CIGS) solar cells can potentially address the issues of polycrystalline CIGS (poly-CIGS) solar cells, but their conversion efficiency has not been widely studied. We fabricated epi-CIGS layers using techniques developed for high-efficiency ploy-CIGS solar cells such as Ga grading, Na doping, and heat-light soaking. Here, scanning transmission electron microscopy and secondary ion mass spectrometry were used to compare the structural characteristics of poly- and epi-CIGS solar cells with conversion efficiencies of more than 21%. Both types of solar cells had similar Ga gradient profiles, and abrupt interfaces were observed between the CIGS and Mo, CIGS and GaAs, and CdS and CIGS layers. The poly-CIGS layer had a higher Na concentration than the epi-CIGS layer because the grain boundaries of the former included high concentrations of Na ions. Meanwhile, the Na ions in the epi-CIGS layer promoted the interdiffusion of In and Ga. For both types of solar cells, heat-light soaking increased the carrier concentration by more than 1 × 1017 cm−3. These observations suggest that grain boundaries are not the main factor limiting the conversion efficiency of poly-CIGS solar cells.

Effect of Time and Voltage on the Electrophoresis Deposition of Zinc Oxide Thin Films for Photovoltaic Applications

Electrophoretic deposition is a straightforward, environmentally friendly, and cost-effective technique for depositing and synthesizing nanomaterials, particularly nanofilms of semiconductors. Key parameters in electrophoresis include deposition time and voltage. Zinc oxide, a semiconductor of significant interest in solar energy research, possesses favorable characteristics, notably, a band gap value of approximately 3.33 eV. In the realm of dye-sensitized solar cells, which represent the third generation of solar cells, zinc oxide has emerged as a compelling choice for a photoanode. This study focused on depositing thin films of zinc oxide through electrophoresis and applying them as photoanodes in dye solar cells. The results demonstrated that the electrodeposited films exhibited good reflectance in the visible spectrum (~60–90%), a band gap energy of 3.28 eV, and an incident photon conversion efficiency of approximately 4.48% for the electrodeposited film at 80 V for 5 min.

Tuning the crystalline orientation of quasi 1D anisotropic Sb2Se3 as a function of growth temperature for thin film photovoltaic applications

Antimony selenide (Sb2Se3) shows excellent photon absorption in the visible region and hence gaining tremendous attention from the last decade for thin film photovoltaics. Also, it has unique one-dimensional crystal structure and simple binary composition. However, the growth of Sb2Se3 thin films with its predominant orientation along [hk1] to make use of easy electrical charge transport seems challenging due to various governing growth parameters. In this work, we have studied the role of growth temperature (between 200 ℃ and 320 ℃) in the crystalline orientation of Sb2Se3 thin films on glass substrates via close-space thermal evaporation. In addition to growth orientation, we have investigated the effect of growth temperature on the surface morphology, elemental composition, film thickness, and optical properties of Sb2Se3 thin films. Electrical properties and photoresponse were measured on [hkl] and [hk0] oriented films to understand the effect of anisotropy and it is inferred that [hk1] oriented film as a favorable one for the charge transport. Also, the photoresponse results showed fair photoconductance under white light illumination and zero applied bias.

Compositional Transformation and Impurity‐Mediated Optical Transitions in Co‐Evaporated Cu2AgBiI6 Thin Films for Photovoltaic Applications

AbstractQuaternary copper‐silver‐bismuth‐iodide compounds represent a promising new class of wide‐bandgap (2 eV) semiconductors for photovoltaic and photodetector applications. In this study, vapor phase co‐evaporation is utilized to fabricate Cu2AgBiI6 thin films and photovoltaic devices. The findings show that the properties of vapor‐deposited films are highly dependent upon processing temperature, exhibiting increased pinhole density and transforming into a mixture of quaternary, binary, and metallic phases depending on the post‐deposition annealing temperature. This change in phase is accompanied by an enhancement in photoluminescence (PL) intensity and charge‐carrier lifetime, along with the emergence of an additional absorption peak at high energy (≈3 eV). Generally, increased PL is a desirable property for a solar absorber material, but this change in PL is ascribed to the formation of CuI impurity domains, whose defect‐mediated optical transition dominates the emission properties of the thin film. Via optical pump terahertz probe spectroscopy, it is revealed that CuI impurities hinder charge‐carrier transport in Cu2AgBiI6 thin films. It is also revealed that the predominant performance limitation in Cu2AgBiI6 materials is the short electron‐diffusion length. Overall, the findings pave the way for potential solutions to critical issues in copper‐silver‐bismuth‐iodide materials and indicate strategies to develop environmentally compatible wide‐bandgap semiconductors.

Rear Surface Passivation for Ink‐Based, Submicron CuIn(S, Se)2 Solar Cells

AbstractA N, N‐dimethylformamide and thiourea‐based route is developed to fabricate submicron (0.55 and 0.75 µm) thick CuIn(S,Se)2 (CISSe) thin films for photovoltaic applications, addressing challenges of material usage, throughput, and manufacturing costs. However, reducing the absorber film thickness below 1 µm in a regular CISSe solar cell decreases the device efficiency due to losses at the highly‐recombinative, and mediocre‐reflective Mo/CISSe rear interface. For the first time, to mitigate the rear recombination losses, a novel rear contacting structure involving a surface passivation layer and point contact openings is developed for solution processed CISSe films and demonstrated in tangible devices. An atomic layer deposited Al2O3 film is employed to passivate the Mo/CISSe rear surface while precipitates formed via chemical bath deposition of CdS are used to generate nanosized point openings. Consequently, Al2O3 passivated CISSe solar cells show an increase in the open‐circuit voltage (VOC) and short‐circuit current density when compared to reference cells with equivalent absorber thicknesses. Notably, a VOC increase of 59 mV contributes to active area efficiencies of 14.2% for rear passivated devices with 0.75 µm thick absorber layers, the highest reported value for submicron‐based solution processed, low bandgap CISSe solar cells.

Formation and detection of secondary crystalline phases in Cu2SnS3 thin films for photovoltaic applications

Formation and detection of secondary crystalline phases in Cu2SnS3 thin films for photovoltaic applications

Exploration of Cd1−xZnxSe as a window layer for CIGS based solar cell with PEDOT: PSS as back surface field layer

This research investigates the potential of Cd1−xZnxSe thin film for photovoltaic applications. The electrical behavior of CIGS based solar cell is examined with the novel Cd1−xZnxSe as buffer layer material by Solar Cell Capacitance Simulator (SCAPS). The tunability of Cd1−xZnxSe facilities to reduce the defects between absorber and buffer layer by determining the ideal conduction band offset. It is revealed that cross-over occurs between the p-type absorber and the metal back contact if the metal work function is below 4.6 eV. In this research, a thin PEDOT: PSS back surface (BSF) layer was integrated which enhances the device efficiency from 22.5 percent to 28.32% while retaining the metal work function at 5.1 eV. The trade-off between the use of metal having higher work function and inclusion of heavily doped BSF layer is one of the important findings of this research. These findings pave the way for Cd1−xZnxSe to be commercially used as a buffer layer material for CIGS solar cell.

Comprehensive structural and surface investigation of Sb2Se3 thin-films

Earth-abundant antimony selenide (Sb2Se3) is a promising material for the thin-film photovoltaic applications due to its desirable optoelectronic properties and suitable band gap. In this work, we present a comprehensive study on the structural and surface properties of Sb2Se3 thin-films for the potential applications in solar cells. The Sb2Se3 samples were grown on Si (100) substrate and at different substrate temperatures using radio frequency (RF) magnetron sputtering. The XRD diffractogram exhibits that Sb2Se3 is the predominant phase in all the samples, whereas the TEM measurements confirm the nanocrystalline nature of the samples. Raman spectroscopy measurements in the range of 30–500 cm−1 displays the Raman shifts at 148, 190 and 206 cm−1, which confirms the presence of the Sb2Se3 phase. The average surface roughness and grain size were obtained via surface topography with the help of the high-resolution AFM images. The EDS spectra revealed the presence of both Se and Sb as constituent elements in all the samples. The deconvolution of XPS spectra of Se 3p and Sb 3d core level disclose the Sb+3 and Se−2 oxidation state and further confirms the presence of Sb2Se3 phase. The XPS and EDS measurements predict that there is loss of Se during the deposition and it could have adverse effects on the performance of Sb2Se3 solar cell devices.

Study of electrical properties of PBDB-T-2Cl based ternary thin films for photovoltaic applications

Study of electrical properties of PBDB-T-2Cl based ternary thin films for photovoltaic applications

Impact of temperature difference on the features of spray deposited yttrium doped cobalt selenide (YCoSe) thin films for photovoltaic application

In this investigation, spray deposited yttrium doped cobalt selenide (YCoSe) thin materials were synthesized in soda lime glass and the impact of substrate temperature (140 oC, 160 oC, 180 oC and 200 oC) on their elemental composition, surface morphology, structural, electrical and optical properties were investigated using scanning electron microscopy-SEM X-ray diffraction –XRD, four-point probe and UV-VIS spectrophotometer respectively. The EDX plots of the deposited undoped and Y-doped cobalt selenide revealed the major elements: cobalt, selenium and yttrium. This confirms the deposition of CoSe and Y-doped CoSe thin materials. The morphology of undoped CoSe thin materials was very rough containing randomly oriented non-uniform thin particles while addition of Y dopant (0.1 mol%) at substrate temperature of 140 oC gave a homogenous distribution of compact rectangular-like nanograins. The XRD result shows that the films are cubic polycrystalline in nature and the film grown at substrate temperature of 180 oC was seen to give the most excellent crystalline quality and a preferential orientation along (111) direction. From electrical results it was observed that increase in substrate temperature increased the film thickness with decreased resistivity and increased conductivity. The optical properties were found to vary with substrate temperature despite the fact that the variation was not totally linear, as the film deposited at substrate temperature of 160 oC deviated from the linearity in all the optical properties. The energy band gap of the deposited samples ranges from 1.25 eV–1.75 eV. The materials produced could be used in the production of photovoltaic devices.

Synthesis of magnesium doped manganese oxide (MnMgO) thin films for photovoltaic applications

A straightforward, inexpensive chemical technique of spray pyrolysis was employed to deposit MnO thin films on glass substrates at suitable flow parameters. In this investigation, spray pyrolysis was used to successfully deposit magnesium-doped manganese oxide thin films at various molar concentrations 0, 0.2, and 0.4. Using X-ray powder diffraction, FE-SEM and UV–Visible spectrophotometry methods, the produced thin film was evaluated to investigate its structural, morphological and optical attributes regarding the variation atomic percentage of magnesium, by maintaining a constant thin film's thickness. The MgMnO film's XRD pattern revealed that it is polycrystalline in nature. The growing magnesium doping is responsible for the noticeable (200) plane. The increase in surface roughness of prepared thin films has been studied with increasing in magnesium doping concentration. By using The magnesium doping of the films had an impact on their absorption. The magnesium doping concentration resulted in a modest reduction in the bandgap of the MgMnO thin films, which is advantageous for solar applications.

Physical properties of Ag3SbS3 thin films for photovoltaic applications

Ag3SbS3 thin films have been prepared by heating multilayers of glass/Sb2S3/Ag at different temperatures. Thin film of Sb2S3 were deposited on glass substrates using chemical bath deposition technique. Thermal evaporation of silver followed by annealing at 300 and 350°C were carried out to synthetize Ag3SbS3 thin films. XRD spectra showed the formation of Ag3SbS3 thin films at 300 and 350 °C with a micro-strain and grain size of 1.8 x 10-3 and 21 nm, respectively. Electrical conductivity in the range of 10-4 – 10-5 (Ωcm)-1 and a band gap of 1.3 eV were obtained.

Investigation and optimization of an effective fabrication process to develop a high-quality CZTS thin layer for photovoltaic applications

Despite its outstanding advantages, its relatively low practical efficiency has prevented CZTS from replacing CIGS. The most important reason for this drawback is known to be the poor crystallization and high porosity of the produced CZTS thin films, causing defect-related recombination. In this work, an organic-based sol-gel method has been used to develop CZTS thin films and several parameters have been examined to optimize the developed thin film quality. Controlled parameters include the molar ratio of precursor solution, drying atmosphere of the samples, thermal annealing, and sulfurization concurrent to thermal annealing. The effect of each parameter was experimentally evaluated using the produced samples' structural, morphological, optical, and electrical characterization. The experimental details of the synthesis and post-processing procedures are presented in addition to the results of performed characterizations such as XRD, UV–vis, Raman spectroscopy, SEM micrographs, EDS analysis, and sheet resistance, which are discussed in this article. Finally, the optimized thin film's response to different wavelengths was evaluated and exhibited an excellent response to the applied wavelengths. The findings of this study would be useful in the development of high-quality CZTS thin films for photovoltaic applications.

Investigating the effects of bismuth doping on the structural, optical, and electrical properties of Cu2ZnSnS4 thin films for photovoltaic applications

Investigating the effects of bismuth doping on the structural, optical, and electrical properties of Cu2ZnSnS4 thin films for photovoltaic applications

On the role of sodium and copper off‐stoichiometry in Cu (In,Ga)S2 for photovoltaic applications: Insights from the investigation of more than 500 samples

AbstractThe present article discusses the investigation of CuIn1−xGaxS2 (CIGS) thin films for photovoltaic applications. For decades, a Cu‐rich composition has been used to create solar cells with efficiencies of up to 13.5%; however, interest in chalcopyrite sulfide has recently been revived due to its high and adjustable bandgap, making it a serious candidate as a top cell in tandem configurations. Although chalcopyrite selenides share many properties with CIGS thin films, crucial differences have been reported. To further understand these materials, we studied more than 500 samples of absorbers and resulting solar cells. First, we found that the compositional window for obtaining single‐phase CIGS thin films with a three‐stage co‐evaporation process is very narrow. Second, we reported that a combination of low copper content and sodium addition during growth is required to maximize the photoluminescence intensity (i.e., to minimize the absorber‐related open‐circuit voltage losses). Finally, we showed that solar cell performance and stability depend not only on absorber quality but also on phenomena at interfaces (absorber/buffer and grain boundaries). Altogether, we formulate growth recommendations for the manufacture of stable CIGS/CdS solar cells with state‐of‐the‐art efficiency.

Atomic layer deposition of Cu2O using copper acetylacetonate

Cu2O is an important p-type semiconductor material with applications in thin-film transistors, photovoltaics, and water splitting. For such applications, pinhole-free and uniform thin films are desirable, thus making atomic layer deposition (ALD) the ideal fabrication technique. However, existing ALD Cu precursors suffer from various problems, including limited thermal stability, fluorination, or narrow temperature windows. Additionally, some processes result in CuO films instead of Cu2O. Therefore, it is important to explore alternative precursors and processes for ALD of Cu2O thin films. In this work, we report the successful deposition of Cu2O using copper acetylacetonate as a precursor and a combination of water and oxygen as reactants at 200 °C. Saturation of the deposition rate with precursor and reactant dose time was observed, indicating self-limiting behavior, with a saturated growth-per-cycle of 0.07 Å. The Cu2O film was polycrystalline and uniform (RMS roughness ∼2 nm), with a direct forbidden bandgap of 2.07 eV and a direct allowed bandgap of 2.60 eV.