Efficient Thin Film Solar Cells Research Articles

Enhancing the efficiency of Cu2Te thin-film solar cell with WS2 buffer layer: A simulation study

In this work, the Cd-free tungsten disulfide (WS2) material as the buffer layer is proposed in the copper telluride (Cu2Te)-based heterojunction solar structure. The Cu2Te thin-film photovoltaic organization of Ni/Cu2Te/CdS or WS2/SnO2:F(FTO)/Al has been designed and evaluated numerically by using the One Dimensional Solar Cell Capacitance Simulator. The WS2 buffer layer provides a significant improvement in the output parameters of the Cu2Te solar device compared to the cell with the CdS buffer. A high efficiency of 24.23% with Voc of 0.68 V, Jsc of 42.95 mA/cm2, and FF of 82.77% is obtained for the designed Cu2Te-based solar cell with WS2 buffer. The ‘spike-like’ band structure formed at Cu2Te/WS2 interface plays an important function in the enhancement of the outputs by minimizing carrier recombination. The thicknesses of 0.05 μm for buffer and 1.0 μm for absorber are optimized by considering the low fabrication cost. Moreover, the photovoltaic parameters of the Cu2Te solar cell are evaluated by varying the doping concentration, bulk and interface defects, operative temperature, rear contact work function, and cell resistances. The data outcomes imply that the anticipated Cu2Te-based photovoltaic device with a non-toxic WS2 buffer can be an efficient substitute to the toxic CdS for cost-effective and stable thin-film solar devices.

Rear interface engineering via a facile oxidation process of Mo back contact for highly efficient CZTSSe thin film solar cells

The kesterite-based Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells (TFSCs) are promising absorber material for next-generation TFSCs technology because they exhibit earth-abundant, non-toxic elements and favorable optoelectronic properties. However, the progress and device performance development in CZTSSe TFSCs were limited because of unstable rear interface characteristics near the absorber/molybdenum (Mo) interface, which causes large open-circuit voltage loss. In this study, we report the rear interface engineering of CZTSSe TFSCs to improve device performance by introducing an amorphous thin MoOx intermediate layer by a facile oxidation process. We observed that (i) an amorphous thin MoOx intermediate layer can effectively control the rear interface properties (i.e., inhibiting the formation of Mo(S,Se)2 interfacial layers and voids at CZTSSe/Mo interface) and (ii) the improved device performance in CZTSSe TFSCs with oxidation (w-oxidation) is attributed primarily to the dramatically decreased shunt conductance, formation of large-sized grains within CZTSSe absorber layer, and improved rear interface characteristics. This study presents a simple and low-temperature oxidation process for rear interface engineering of highly efficient kesterite CZTSSe-based TFSCs.

Characterization of Sb2Te3 thin films prepared by electrochemical technique

A conductive and thermally stable material with a high work function is required to produce highly efficient CdTe-based thin film solar cell (TFSC) devices. In this study, we report the growth of layers of polycrystalline, stoichiometric, and compact antimony telluride (Sb2Te3) by using the wet-chemical aqueous electrochemical technique. A three-electrode geometry consisting of a working electrode, a reference electrode, and a counter electrode was used to deposit the Sb2Te3 thin films at a low temperature (60 °C ± 2 °C). The growth potential was optimized through cyclic voltammetric measurements with reference to the Ag/AgCl reference electrode. The structural, morphological, compositional, and electrical properties of the films were studied and correlated. Their prominent Bragg reflections of (103), (016), and (110) verified the growth of the rhombohedral crystal structure of Sb2Te3. The Raman modes Eg and A1g, observed at 119.88 and 161.48 cm−1, respectively, confirmed the formation of the Sb2Te3 compound. Compact grain growth with a void-free and well-adherent layer was observed using scanning electron microscopy. The grain size, surface morphology, and thickness of the Sb2Te3 layers were significantly influenced by variations in the deposition potentials. An EDS analysis of the sample grown at −0.5 V revealed nearly stoichiometric growth (2:3, Sb:Te ratio). The elemental chemical states were studied through XPS analysis. The survey scan confirmed the presence of antimony, tellurium, oxygen, and carbon. The current–voltage characteristics reflected the nearly ohmic nature of the Sb2Te3 thin films. The ideality factor and carrier concentration obtained for the sample grown at −0.5 V exhibited nearly ohmic behaviors, with a high conductivity that was suitable for back-contact between the buffer layer and CdTe for the development of CdS/CdTe solar cells.

Additive strategy to regulate crystallization and charge carrier dynamics of CsBi3I10 towards efficient and stable thin film solar cells

All-inorganic semiconductor CsBi3I10 (CBI) has recently been recognized as promising alternatives to lead-based light harvesting materials. However, poor film quality and high defects greatly limit its photovoltaic performance in solar cell applications. Here, a simple and effective multifunctional additive of lead thiocyanate (Pb(SCN)2) is doped into CBI for tailoring film morphology and optoelectronic properties. Synergistic effects of Pb2+ and pseudohalide SCN- enable fine regulation of CBI crystallization as well as defects passivation, resulting in the formation of high-quality thin film with desirable uniformity, negligible pinholes, high electrical conductivity and remarkable moisture tolerance. The additive Pb(SCN)2 can efficiently alleviate moisture-induced degradation mechanism by inhibiting the phase transition from CBI to Cs3Bi2I9. In addition, the resulting solar cells exhibit significantly enhanced carrier lifetime, reduced charge recombination and increased charge collection yield, leading to a record efficiency of 1.13 % for planar CBI-based thin film solar cells. This work suggests additive engineering is efficient to modulate film properties and solar cell performance, which could be generally applicable to fabricate other Bi-based thin film and optoelectronic devices.

Modification of CuSbS2 Photovoltaic Absorbent Properties via Defect Substitution

CuSbS2 is an earth-abundant alternative absorbent material for thin-film solar cells. However, because of the comparable size of cations in CuSbS2 thin films, atomic disorder occurs, which modifies the Cu/Sb ratio and lowers the efficiency of the solar cells. A similar effect has been observed in previously reported absorbent materials, which could be reduced using extrinsic substitution defects. Although extrinsic substitution defects are crucial for resolving the disorder-related issues, they can strongly modify the structural, electronic, and optical properties of the CuSbS2 absorbent material, which may lower the efficiency of CuSbS2-based thinfilm solar cells. Therefore, herein, first-principle calculations were used to investigate structural, electronic, and optical properties of CuSbS2 with the Te-, Sn-, and Bi-substitution of Sb. The formation energies of the defects were calculated to investigate the stability of the defects at different charge states. Our results revealed that the absorption coefficient is strongly sensitive to structural distortions. Moreover, Sn+2Sb defects cause an indirect-to-direct band gap transformation, which can increase the efficiency of CuSbS2-based thin-film solar cells.

Role of Intrinsic Defects in Enhancing the Photoabsorption Capability of CuZn2AlSe4.

As a promising candidate for low-cost and eco-friendly thin-film photovoltaics, the emerging quaternary chalcogenide based solar cells have experienced rapid advances over the past decade. Here, we propose quaternary semiconducting chalcogenides CuZn2AlSe4 (CZASe) through cross-substitutions (cation mutations). The nonexistence of imaginary modes in the entire Brillouin zone of CZASe represents the inherent dynamic stability of the system. The electronic, optical, and defect properties of stannite CZASe quaternary semiconducting material was systematically investigated using density functional theory calculations. We have found that the chemical-potential control is very important for growing good-quality crystals and also to avoid secondary-phase formations such as ZnSe, Al2ZnSe4, and Cu3Se2. The observed p-type conductivity is mainly due to antisite defect CuZn, which has the lowest formation energy with a relatively deeper acceptor level than that of the Cu vacant site (VCu). The electronic band structures of vacancies and antisite defects by means of hybrid functional calculations show energy band shifting and energy band narrowing or broadening, which eventually tunes the optical band gap and improves the solar energy-conversion performance of semiconducting CZASe. Our results suggest that the stannite CZASe quaternary chalcogenides could be promising candidates for the efficient earth-abundant thin-film solar cells.

Fine adjusting of charge carriers transport in absorber/HTL interface in Sb2(S,Se)3 solar cells

Sb2(S1-x,Sex)3 compounds with tunable band gap values received considerable attention as solar absorber candidates for efficient thin film solar cells. However, the efficiency of Sb2(S,Se)3 solar cells is limited to less than 10.5 %. An investigation into the performance of contact/Hole Transport Layer (HTL)/ Sb2(S,Se)3/Electron Transport Layer (ETL)/contact has been carried out. The efficient transformation of photogenerated carriers in HTL/absorber is essential for efficient Sb2(S, Se)3 solar cells. Three methods have been applied to achieve this goal: changing Se content in the absorber, using HTLs with different valence band maximum, and changing the carrier concentration in HTLs. The relationship between solar cell performance and valence band maximum of the hole transport layer and the change of Se content in the Sb2(S,Se)3 absorber layer was studied. In addition, the effect of HTL carrier concentration on the output efficiency of Sb2(S,Se)3 thin-film solar cells is investigated. When the selenium mole fraction in the Sb2(S,Se)3 layer is around 0.4–0.7 and the valence band maximum of the hole transport layer is around 5.1–5.9 eV, the efficiency is optimal. It has also been found that for the best efficiency, a carrier concentration of 1017 cm−3 or more is needed.

Influence of SnMnO2 window layer on enhancing the performance of CIGSSe thin-film solar cell

In this paper, the thickness and doping concentrations of the double buffer cell-based conventional CIGSSe solar cells are optimized, and alignment of the energy band of the optimized solar cell (ZnMgO/CIGSSe) is carried out, thus obtaining an increase in efficiency from 23.35 % to 27.88 %. Further, a new design is proposed of low cost, low resistivity, minimum absorption coefficient, tunable energy bandgap (3.6–4.44 eV) with tin-doped manganese oxide Sn1−xMnxO2 material (x = 0.5) as a window layer in conventional solar cell design. The thin-film solar cell efficiency has improved from 23.35 % to 29.05 % by aligning the energy bandgap with an optimized thickness and doping concentration. The proposed Sn1−xMnxO2 window layer-based thin-film solar cell is more convenient in instantly absorbing the maximum blue light with reduced recombination loss, increased efficiency and external quantum efficiency. The simulated parameters of the conventional model are compared and validated with the existing conventional solar cells.

(Invited) Photoabsorption and Excitation Energy Transfer in Fluorinated Non-Fullerene Acceptors for Organic Solar Cells

Recently, it was reported that OSCs based on non-fullerene acceptors have shown high photovoltaic performance with over 18% efficiency, being more than the power conversion efficiencies (PCEs) of 13% in OSCs based on fullerene. We considered theoretically the effects of fluorine atoms on the conversion efficiency of organic thin-film solar cells from the electronic analysis of donor/acceptor (D/A) complex interactions for NTz-Teh-FA and FNTz-Teh-FA using DFT. It was confirmed that it differs depending on the side-chain length, and it is necessary to consider the side-chain length. Because the longer the side-chain length, the lighter absorption and increased charge transfer. In the fluorinated acceptor, the polarity around the O atoms at both ends of the main chain was weakened, the twist angle of the molecular structure was reduced, and the light absorption at 600–700 nm was increased in the absorption spectrum. Therefore, it is considered that the fluorinated nonfullerene-type acceptor FNTz-Teh-FA, which has a long side chain, has the best light absorption and charge transfer. Excitation Energy Transfer (EET) calculations show that the Coulomb coupling contributes significantly. In addition, it was confirmed that the fluorinated complex had a higher EET. Therefore, it is considered that the charge separation efficiency is improved. Thus, it is considered that the short-circuit current density (JSC) is improved by improving the internal quantum efficiency (IQE), including the element of the charge separation efficiency.

Electric Field as A Novel Switch to Enhance Optical Absorption Spectra of Defect Blue Phosphorene Thin-films

Improvement of the optical absorption coefficient is essential to enhance the light conversion efficiency of thin-film organic solar cells. Here we report the use of an external electric field as a novel switch to improve the optical absorption capacity of two-dimensional defect blue phosphorene (BlueP) systems. Using the density functional theory with van der Waals functionals, we investigate the structural, electronic, magnetic and optical absorption properties of the pristine, single-vacancy (SV) BlueP thin films, and a BlueP system absorbing a Vanadium adatom. We demonstrate that a SV BlueP layer would exhibit half-metallic and its absorption spectrum under an electric field parallel to the material plane is significantly enhanced in the ultra-violet region. More interestingly, when a Vanadium transition metal is absorbed on a pristine BlueP, the applied electric field perpendicular to the BlueP plane not only doubles the optical absorption coefficient, but also switches ON/OFF the magnetic moments of this system. The prominent red shift of the absorption spectra towards the visible light range under selected polarized directions paves a novel way to engineer solar cell devices with BlueP materials.

X-ray diffraction of photovoltaic perovskites: Principles and applications

Solar cells based on organic–inorganic hybrid perovskite materials have emerged as the most efficient next-generation thin-film solar cells within just a decade of research and show great promise for commercialization. As control of the thin-film microstructure of the perovskite layer is a key factor enabling high photovoltaic efficiency, good stability, and successful up-scaling of high-quality perovskite thin films for commercialization, a reliable and accurate characterization of the thin-film microstructure is paramount. X-ray diffraction (XRD)-based techniques, including conventional laboratory-based XRD and synchrotron-based grazing-incidence wide-angle x-ray scattering, are widely used to probe the microstructure of photovoltaic perovskite thin films. Nevertheless, it is common for these XRD experiments to be poorly executed and diffraction data to be improperly interpreted. This review focuses on principles of XRD techniques and their application for the characterization of the perovskite thin-film microstructure. Fundamentals of XRD techniques are presented with a strong emphasis on best practices in data collection and analysis. Approaches for the reliable and accurate extraction of microstructural information from diffraction data are discussed, including the need for simulating diffraction patterns. Applications of XRD techniques in characterizing perovskite thin films are demonstrated for both three-dimensional and layered hybrid perovskites, covering various microstructural aspects including phase identification and quantification, texture analysis, microstrain, and macrostrain as well as in situ and operando characterization. The additional subtleties and complexities associated with the XRD characterization of layered hybrid perovskites due to a more complex thin-film microstructure are discussed. Common mistakes and pitfalls that lead to misinterpretation of diffraction data are also highlighted.

Optimization of Absorber Layer and Operating Temperature of Copper Indium Gallium Selenide Solar Cells Using Different Metal Contacts

Device simulation was employed to investigate the effect of metal back contact electrodes on the performance of n-type CdS/p-CIGS thin film solar cells using varying thicknesses of absorber layer at operating temperature of 300K. The effect of working temperatures was also studied from 300K to 400K in steps of 10K. The simulations were carried out using standard solar cell capacitance simulator (SCAPS) 3.3.03 version software. The results showed better efficiencies at the optimized thickness of 3µm for all the back contact electrodes under study. The maximum efficiencies of 17.5 %, 15.5 %, 11.5 %, 3.5 % and 3 % were estimated for CIGS thin film solar cell at 300 K for platinum, gold, cobalt, silver and copper back contact electrodes respectively. The efficiency decreases as the operating temperatures increases from 300 K to 400 K. It is recommended that the optimized thickness of 3 µm is appropriate as absorber layer for efficient and cost effective CIGS thin film solar cells for economic reasons.

Defect physics of the quasi-two-dimensional photovoltaic semiconductor GeSe

GeSe has recently emerged as a photovoltaic absorber material due to its attractive optical and electrical properties as well as earth abundancy and low toxicity. However, the efficiency of GeSe thin-film solar cells (TFSCs) is still low compared to the Shockley–Queisser limit. Point defects are believed to play important roles in the electrical and optical properties of GeSe thin films. Here, we perform first-principles calculations to study the defect characteristics of GeSe. Our results demonstrate that no matter under the Ge-rich or Se-rich condition, the Fermi level is always located near the valence band edge, leading to the p-type conductivity of undoped samples. Under Se-rich condition, the Ge vacancy (VGe) has the lowest formation energy, with a (0/2–) charge-state transition level at 0.22 eV above the valence band edge. The high density (above 1017 cm−3) and shallow level of VGe imply that it is the p-type origin of GeSe. Under Se-rich growth condition, Sei has a low formation energy in the neutral state, but it does not introduce any defect level in the band gap, suggesting that it neither contributes to electrical conductivity nor induces non-radiative recombination. In addition, Gei introduces a deep charge-state transition level, making it a possible recombination center. Therefore, we propose that the Se-rich condition should be adopted to fabricate high-efficiency GeSe solar cells.

Efficiency improvement of CIGS solar cells using RF sputtered TCO/Ag/TCO thin-film as prospective buffer layer

In this paper, TCO (Transparent Conductive Oxide) incorporating ultrathin Ag intermediate film is proposed as a new buffer layer to enhance the efficiency of CIGS thin-film solar cells (TFSCs). In this regard, versatile multilayer thin-films based on ZnO/Ag/ZnO and ITO/Ag/ITO structures were deposited on glass using RF magnetron sputtering technique to determine the optoelectronic parameters of the multilayer structures. The elaborated samples were then characterized using SEM, EDS, XRD, and UV–Visible absorption spectroscopy techniques to investigate the structure morphological, optical, and electronic properties. The deposited multilayer thin-films showed amorphous-like structure and exhibited a broadband absorbance over the visible and even NIR spectrum ranges, indicating its potential application as alternative buffer layers for thin-film solar cells. In this context, TCO/Ag/TCO/CIGS solar cells have been numerically investigated using the deposited multilayer optoelectronic properties. It was revealed that the estimated efficiency of the ZnO/Ag/ZnO/CIGS-based solar cell could reach 18.5% with an open circuit voltage of 0.7 V and a short-circuit current density of 34.8 mA/cm2. The performances exhibited by the investigated solar cell demonstrated that ZnO/Ag/ZnO multilayer can be used as an alternative to the conventional CdS buffer layer for developing high-performance non-toxic CIGS solar cells.

Probing Charge Generation Efficiency in Thin-Film Solar Cells by Integral-Mode Transient Charge Extraction.

The photogeneration of free charges in light-harvesting devices is a multistep process, which can be challenging to probe due to the complexity of contributing energetic states and the competitive character of different driving mechanisms. In this contribution, we advance a technique, integral-mode transient charge extraction (ITCE), to probe these processes in thin-film solar cells. ITCE combines capacitance measurements with the integral-mode time-of-flight method in the low intensity regime of sandwich-type thin-film devices and allows for the sensitive determination of photogenerated charge-carrier densities. We verify the theoretical framework of our method by drift-diffusion simulations and demonstrate the applicability of ITCE to organic and perovskite semiconductor-based thin-film solar cells. Furthermore, we examine the field dependence of charge generation efficiency and find our ITCE results to be in excellent agreement with those obtained via time-delayed collection field measurements conducted on the same devices.

Interface Etching Leads to the Inversion of the Conduction Band Offset between the CdS/Sb2Se3 Heterojunction and High-Efficient Sb2Se3 Solar Cells

Antimony selenide (Sb2Se3) has gained extensive attention owing to its excellent properties of stability and optoelectronic characteristics. However, the band-gap alignment of CdS/Sb2Se3 heterojunction is still a significant bottleneck in the improvement of the efficiency of Sb2Se3 thin-film solar cells. In this study, the quality of a vapor transport deposition (VTD)-processed Sb2Se3 thin film is improved by ammonia etching, wherein the surface potential of the CdS buffer layer is modified and the band-gap alignment of CdS/Sb2Se3 is changed from a “clifflike” to a “spikelike” structure. Moreover, the growth orientation of the Sb2Se3 absorber is tailored. Finally, the reduced carrier recombination, improved band-gap structure, and enhanced crystal orientation lead to the fabrication of a Sb2Se3 solar cell with the best efficiency of 7.48% in this work, which is comparable with the highest efficiency of VTD-processed Sb2Se3 thin-film solar cells. This is expected to provide a valuable reference for the future development of Sb2Se3 thin-film solar cells and other photoelectronic devices.

In situ metallic copper incorporation into novel g-C3N4/ZnWO4 nanocomposite semiconductor for efficient thin film solar cell application

Developing a noble metal-based solar energy conversion device is important in energy research. Again, nanocomposites consisting metal oxide-organic framework have received tremendous attention due to their excellent charge carrier transportability. Here, we have designed a nanocomposite by mixing π-conjugated sp2 hybridized g-C3N4 with ZnWO4 nanorods in which, Cu has been loaded. The red shift of the surface plasmon resonance (SPR) peak of Cu in case of g-C3N4/Cu/ZnWO4 (CCZ) is reflected in the photoluminescence (PL) lifetime data [CCZ (τ = 8.1 ns) > ZnWO4 (τ = 6.6 ns)]. Also, the PL intensity is found to get diminished for the composite owing to the delocalization of photoexcited electrons from the conduction band of g-C3N4 to the plasmonic metal (reservoir) through ZnWO4. Thin-film semiconductor (SC) photovoltaic (PV) devices on ITO coated surface have been successfully fabricated by spin coating the as-synthesized nanocomposites in conjunction with PEDOT: PSS and the power conversion efficiency (PCE) got improved from 1.8% (ZnWO4) to 8.4% (CCZ). Further, incident photon to current conversion efficiency (IPCE) for as-designed devices were obtained to be 73% (CCZ) > 47% (g-C3N4/ZnWO4) > 10% (ZnWO4) at 475 nm. In addition, CCZ has demonstrated high thermal stability without affecting the PCE value.

11.39% efficiency Cu2ZnSn(S,Se)4 solar cells from scrap brass

Kesterite Cu2ZnSn(S,Se)4 is one of the most promising next-generation thin-film photovoltaic materials. Along with the efficiency advancement of kesterite solar cells, a cost-effective fabrication process with low carbon footprint plays an increasingly important role considering the near-future industrialization of CZTSSe solar cells. In this study, we proposed an environmental friendly process to recover copper and zinc from the scrap brass, which can be directly used as the precursor salts to fabricate efficient CZTSSe thin-film solar cells. The best power conversion efficiency (PCE) of the device using the proposed eco-friendly process is 11.39% (certified at the National PV Industry Measurement and Testing Center) for CZTSSe solar cells.

Opto-Magnetic and Morphological Properties of the Quaternary CZCr+2TS Semiconductor

Recently, Cu2ZnSnS4 (CZTS) chalcogenide has been given extra attention in CZTS thin-film solar cells. In order to enhance the conversion efficiency of CZTS thin-film solar cells, the physical properties of CZTS semiconductor have been improved by incorporating Cr elements into the CZTS semiconductor using the solvothermal method. The experimental results showed that the Cr[Formula: see text] ion had stronger hybridization and are more effective on energy storage than Zn[Formula: see text] ion. XRD pattern revealed that the crystal structure of CCrTS compound has high crystallinity and low distortion. Raman analysis indicated the structural transition from kesterite CZTS to stannite CCrTS occurred in the multicomponent CZCrTS samples with Cr content ([Formula: see text]) in the range of 0.75–1. In addition, VSM and UV–Vis absorption spectrum showed the CCrTS compound had a new opto-magnetic property and exhibit a strong ferromagnetic ordering at room temperature. Where the magnetic energy resulted from incorporating Cr[Formula: see text] ion in the Cu2ZnSnS4 has been stored and distributed in abroad absorption band in UV–vis ranges And Also, led to a decrease in the direct bandgap in the ranges of 1.54–1.25[Formula: see text]eV. FE-SEM showed that by replacing Cr[Formula: see text] ion with Zn[Formula: see text] ion, the particle size was decreased as a result of converting the applied strain from compressive strain to tensile strain in the CZCr[Formula: see text]TS resulting in decreasing the unit cell volume and the crystal size. This shows that incorporating Cr[Formula: see text] ions into CZTS compound may be well suitable for fabricating it as an absorber layer in CZTS thin-film solar cells.

Smooth Cu electrodeposition for Cu(In, Ga)Se2 thin-film solar cells: Dendritic clusters elimination by Ag buffer layer

Smooth and compact Cu(In, Ga)Se2 (CIGSe) thin film is critical to prepare high-quality solar cells. However, the ”dendritic” morphology of Cu tends to form on Mo leading to a nonuniform Cu distribution during the electrodeposition process, which affects the uniformity of CIGSe and device performance. In this work, Ag was used as the underlying buffer layer and Cu was electrodeposited on Ag film instead of Mo film. By adjusting deposition parameters, smooth and compact Ag layer was obtained on the Mo surface. With the Ag buffer layer, the ”dendritic” Cu on Mo was successfully eliminated. The electrodeposited Ag/Cu/In/Ga metal precursors were annealed in Se-containing atmosphere at 450 °C∼550 °C for 15min to prepare (Ag, Cu)(In, Ga)Se2 (ACIGSe) absorbers. Compared with the CIGSe absorber, the crystallinity of the ACIGSe absorber was improved. The VOC, JSC, FF and efficiency of ACIGSe solar cells were improved compared with CIGSe solar cells. Ultimately, an 11.73% efficiency of ACIGSe thin-film solar cells was obtained.