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Orientation control of Cu(In,Ga)Se-2 (CIGS) thin film could be critical to achieve conversion efficiency of CIGS solar cells that exceeds 20%. The preferred orientation of CIGS thin film is investigated here by modifying the surface of an underlying Mo film. The orientation and surface morphology of the Mo film were modified by varying the depositi...
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... the latter case, the number of grains with the (300) orientation increases. Figure 6 shows XRD patterns of CIGS films, deposited on the MoSe 2 /Mo/glass substrates. A CIGS film with the (112)-preferred orientation was grown on the (006)-preferred (In,Ga) 2 Se 3 film, while a CIGS film with the (220)/(204)-preferred orientation was grown on the less (006)-preferred (In,Ga) 2 Se 3 film. ...
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... (220)/(204)-oriented CIGS film grew on the surface Mo layer with small and rough grains that was deposited at 10 mTorr. Figure 7 shows SEM plane images of CIGS films grown on Mo films with surface Mo layers deposited at 1 and 10 mTorr. The mor- phology of the CIGS film deposited on the surface Mo layer grown at 1 mTorr shows many faceted grains (Fig. 6a), while the CIGS film on the surface Mo layer grown at 10 mTorr shows many round grains (Fig. 6b). The grain size in Fig. 6a is larger than that in Fig. 6b. It is apparent that the CIGS grains in Fig. 6b are more densely connected than those in Fig. 6a and the surface of the CIGS film in Fig. 6b is smoother than that in Fig. 6a. Figure ...
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... deposited at 10 mTorr. Figure 7 shows SEM plane images of CIGS films grown on Mo films with surface Mo layers deposited at 1 and 10 mTorr. The mor- phology of the CIGS film deposited on the surface Mo layer grown at 1 mTorr shows many faceted grains (Fig. 6a), while the CIGS film on the surface Mo layer grown at 10 mTorr shows many round grains (Fig. 6b). The grain size in Fig. 6a is larger than that in Fig. 6b. It is apparent that the CIGS grains in Fig. 6b are more densely connected than those in Fig. 6a and the surface of the CIGS film in Fig. 6b is smoother than that in Fig. 6a. Figure 8 shows AES depth profiles of CIGS/Mo films with different surface Mo layers. The Ar-ion ...
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... 7 shows SEM plane images of CIGS films grown on Mo films with surface Mo layers deposited at 1 and 10 mTorr. The mor- phology of the CIGS film deposited on the surface Mo layer grown at 1 mTorr shows many faceted grains (Fig. 6a), while the CIGS film on the surface Mo layer grown at 10 mTorr shows many round grains (Fig. 6b). The grain size in Fig. 6a is larger than that in Fig. 6b. It is apparent that the CIGS grains in Fig. 6b are more densely connected than those in Fig. 6a and the surface of the CIGS film in Fig. 6b is smoother than that in Fig. 6a. Figure 8 shows AES depth profiles of CIGS/Mo films with different surface Mo layers. The Ar-ion sputtering rate of AES was 80 ∼ 90 ...
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... CIGS films grown on Mo films with surface Mo layers deposited at 1 and 10 mTorr. The mor- phology of the CIGS film deposited on the surface Mo layer grown at 1 mTorr shows many faceted grains (Fig. 6a), while the CIGS film on the surface Mo layer grown at 10 mTorr shows many round grains (Fig. 6b). The grain size in Fig. 6a is larger than that in Fig. 6b. It is apparent that the CIGS grains in Fig. 6b are more densely connected than those in Fig. 6a and the surface of the CIGS film in Fig. 6b is smoother than that in Fig. 6a. Figure 8 shows AES depth profiles of CIGS/Mo films with different surface Mo layers. The Ar-ion sputtering rate of AES was 80 ∼ 90 nm/min. The Mo and Se diffusion ...
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... deposited at 1 and 10 mTorr. The mor- phology of the CIGS film deposited on the surface Mo layer grown at 1 mTorr shows many faceted grains (Fig. 6a), while the CIGS film on the surface Mo layer grown at 10 mTorr shows many round grains (Fig. 6b). The grain size in Fig. 6a is larger than that in Fig. 6b. It is apparent that the CIGS grains in Fig. 6b are more densely connected than those in Fig. 6a and the surface of the CIGS film in Fig. 6b is smoother than that in Fig. 6a. Figure 8 shows AES depth profiles of CIGS/Mo films with different surface Mo layers. The Ar-ion sputtering rate of AES was 80 ∼ 90 nm/min. The Mo and Se diffusion profiles at 1 and 10 mTorr are different, ...
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... of the CIGS film deposited on the surface Mo layer grown at 1 mTorr shows many faceted grains (Fig. 6a), while the CIGS film on the surface Mo layer grown at 10 mTorr shows many round grains (Fig. 6b). The grain size in Fig. 6a is larger than that in Fig. 6b. It is apparent that the CIGS grains in Fig. 6b are more densely connected than those in Fig. 6a and the surface of the CIGS film in Fig. 6b is smoother than that in Fig. 6a. Figure 8 shows AES depth profiles of CIGS/Mo films with different surface Mo layers. The Ar-ion sputtering rate of AES was 80 ∼ 90 nm/min. The Mo and Se diffusion profiles at 1 and 10 mTorr are different, although no apparent MoSe 2 layer can be observed in ...
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... layer grown at 1 mTorr shows many faceted grains (Fig. 6a), while the CIGS film on the surface Mo layer grown at 10 mTorr shows many round grains (Fig. 6b). The grain size in Fig. 6a is larger than that in Fig. 6b. It is apparent that the CIGS grains in Fig. 6b are more densely connected than those in Fig. 6a and the surface of the CIGS film in Fig. 6b is smoother than that in Fig. 6a. Figure 8 shows AES depth profiles of CIGS/Mo films with different surface Mo layers. The Ar-ion sputtering rate of AES was 80 ∼ 90 nm/min. The Mo and Se diffusion profiles at 1 and 10 mTorr are different, although no apparent MoSe 2 layer can be observed in the AES profile. Existing MoSe 2 on the ...
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... faceted grains (Fig. 6a), while the CIGS film on the surface Mo layer grown at 10 mTorr shows many round grains (Fig. 6b). The grain size in Fig. 6a is larger than that in Fig. 6b. It is apparent that the CIGS grains in Fig. 6b are more densely connected than those in Fig. 6a and the surface of the CIGS film in Fig. 6b is smoother than that in Fig. 6a. Figure 8 shows AES depth profiles of CIGS/Mo films with different surface Mo layers. The Ar-ion sputtering rate of AES was 80 ∼ 90 nm/min. The Mo and Se diffusion profiles at 1 and 10 mTorr are different, although no apparent MoSe 2 layer can be observed in the AES profile. Existing MoSe 2 on the Mo/CIGS surface was reported by Wada ...
Citations
... The CIGS film with the (112) preferred orientation was reported to have a high photoexcited carrier recombination [38]. Shin et al. found that a CIGS absorber with a (220) preferred orientation was more efficient (16.36%) than the CIGS absorber with the (112) preferred orientation [39]. Londhe et al., who reported the deposition of the CIGS light absorber by electrodeposition [40], observed that the CIGS deposited at −1.6 V had a large grain size with (220) preferred orientation and relatively high efficiency (~9.07%), while that deposited at −0.9 V had a small grain with (112) preferred orientation and lower CIGS device efficiency (~4.90%) [40]. ...
Heterojunction Cu(In,Ga)Se2 (CIGS) solar cells comprise a substrate/Mo/CIGS/CdS/i-ZnO/ZnO:Al. Here, Al-doped zinc oxide (AZO) films were deposited by magnetron sputtering, and the substrate temperature was optimized for CIGS solar cells with two types of CIGS light absorbers with different material properties fabricated by three-stage co-evaporation and two-step metallization followed by sulfurization after selenization (SAS). The microstructure and optoelectronic properties of the AZO thin films fabricated at different substrate temperatures (150–550 °C) were analyzed along with their effects on the CIGS solar cell performance. X-ray diffraction results confirmed that all the deposited AZO films have a hexagonal wurtzite crystal structure regardless of substrate temperature. The optical and electrical properties of the AZO films improved significantly with increasing substrate temperature. Photovoltaic performances of the two types of CIGS solar cells were influenced by changes in the AZO substrate temperature. For the three-stage co-evaporated CIGS cell, as the sputter-deposition temperature of the AZO layer was raised from 150 °C to 550 °C, the efficiencies of CIGS devices decreased monotonically, which suggests the optimum AZO deposition temperature is 150 °C. In contrast, the cell efficiency of CIGS devices fabricated using the two-step SAS-processed CIGS absorbers improved with increasing the AZO deposition temperature from 150 to 350 °C. However, the rise in AZO deposition temperature to 550 °C decreased the cell efficiency, indicating that the optimum AZO deposition temperature was 350 °C. The findings of this study provide insights for the efficient fabrication of CIGS solar cells considering the correlation between CIGS absorber characteristics and AZO layer deposition temperature.
... CIGS films were deposited on the Mo-coated substrates using a three-stage process by a co-evaporation system [9][10][11]. In the first stage, an (In,Ga) 2 Se 3 precursor layer with 1 mm thickness was grown at 350°C by co-evaporation of In, Ga, and Se. ...
... With an increase in the Se rates during the three-stage process, it has been reported that the preferred orientation (220/204) of the CIGS films can be achieved [35,37,42,43,46,55]. Furthermore, studies [46] have indicated that Mo-coated substrates [56][57][58][59], Na contents [57,59], and Cu contents [59] were the controlling factors of the preferred orientation (220/204) for CIGS films as well. Additionally, the properties of (In,Ga) 2 Se 3 precursors also played a crucial role in obtaining the preferred orientation (220/204) [43,47,56,57]. ...
... Furthermore, studies [46] have indicated that Mo-coated substrates [56][57][58][59], Na contents [57,59], and Cu contents [59] were the controlling factors of the preferred orientation (220/204) for CIGS films as well. Additionally, the properties of (In,Ga) 2 Se 3 precursors also played a crucial role in obtaining the preferred orientation (220/204) [43,47,56,57]. For our CIGS films deposited by the single-stage process, the Cu contents were kept almost the same, and there was no Ga grading within the films. ...
Cu(In,Ga)Se2 (CIGS) films were prepared by a single-stage co-evaporation process at Se flux rates of 10 Å s⁻¹, 20 Å s⁻¹, and 30 Å s⁻¹ and substrate temperatures ranging from 400 °C to 500 °C. The flux rates of the Cu, In, Ga, and Se were kept constant throughout each deposition of the films. The grain sizes, surface morphologies, and crystallinity of the CIGS films improved with increasing substrate temperatures or Se flux rates. The causes of the formation of voids on the surface of CIGS films deposited with a low Se flux rate of 10 Å s⁻¹ at substrate temperatures of 475 °C and 500 °C were addressed. The higher Se flux rates of 20 Å s⁻¹ and 30 Å s⁻¹ repressed the formation of voids for the CIGS films deposited at the relatively higher substrate temperatures of 475 °C and 500 °C. The conversion efficiencies of CIGS solar cells were significantly improved by increasing the substrate temperatures or the Se flux rates, largely contributed from the enhancement of the open-circuit voltage and fill factor because of the restraint of the carrier recombination. The short-circuit current densities were slightly enhanced by the increment of the substrate temperatures or the Se flux rates, resulting from the improved crystalline quality of the CIGS films. Moreover, the EQE results suggest that the effective carrier-diffusion lengths of the films deposited at the relatively high substrate temperatures were increased, leading to the enhancement of the short-circuit current density. The efficiencies of CIGS solar cells prepared with a Se flux rate of 10 Å s⁻¹ improved from 10% to 12.4% when the substrate temperatures increased from 400 °C to 500 °C. The efficiencies of cells deposited at the substrate temperature of 500 °C improved to 15.4% as the Se flux rates increased from 10 Å s⁻¹ to 30 Å s⁻¹.
... CIGS absorber layers were deposited on Mocoated glass substrates using a coevaporation system. 21,22 The composition of the CIGS film was adjusted to be Cu(In 0.7 Ga 0.3 )Se 2 . A 50-nm-thick CdS buffer layer was grown on the CIGS absorber layer using the chemical bath deposition (CBD) process from an alkaline aqueous solution of CdSO 4 , (NH 2 ) 2 CS, and NH 4 OH. ...
Unlabelled:
To reduce the cost of the Cu(In,Ga)Se2 (CIGS) solar cells while maximizing the efficiency, we report the use of an Ag nanowires (NWs) + poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (
Pedot:
PSS) hybrid transparent electrode, which was deposited using all-solution-processed, low-cost, scalable methods. This is the first demonstration of an Ag NWs +
Pedot:
PSS transparent electrode applied to CIGS solar cells. The spin-coated 10-nm-thick
Pedot:
PSS conducting polymer layer in our hybrid electrode functioned as a filler of empty space of an electrostatically sprayed Ag NW network. Coating of
Pedot:
PSS on the Ag NW network resulted in an increase in the short-circuit current from 15.4 to 26.5 mA/cm(2), but the open-circuit voltage and shunt resistance still needed to be improved. The limited open-circuit voltage was found to be due to interfacial recombination that is due to the ineffective hole-blocking ability of the CdS film. To suppress the interfacial recombination between Ag NWs and the CdS film, a Zn(S,O,OH) film was introduced as a hole-blocking layer between the CdS film and Ag NW network. The open-circuit voltage of the cell sharply improved from 0.35 to 0.6 V, which resulted in the best cell efficiency of 11.6%.
... Several studies have reported that the [220/204] orientation of the CIGS more positively affected the solar cell performance than the [112] orientation [11,12]. However, the (220) and (204) planes are actually separate planes included in the tetragonal CIGS structure although they have been usually denoted as "(220/204)" or "(220)/(204)" without any distinction [13,14]. Moreover, the (220) and (204) planes have different atomic arrangements. ...
For better understanding of the structural property of polycrystalline tetragonal Cu(In,Ga)Se2 (CIGS) thin films grown on soda-lime glass, it is necessary to characterize the [220]- and [204]-oriented textures clearly that are related to the different physical properties. However, the distinction between the [220]- and [204]-oriented textures is very difficult because of their nearly identical plane spacings and atomic arrangements. Using x-ray diffraction techniques of high resolution θ-2θ scanning and reciprocal space mapping, we distinguished the [220]- and [204]-oriented textures of CIGS films and observed that the behaviours of [220] and [204] textures independently depended on both substrate nature and Na presence. We report the Na- and substrate-related dependence of the physical properties of the CIGS film was attributed to the independent growth behaviours of the [220] and [204] textures in the CIGS.
... L'orientation cristalline du CIGS dépend fortement des conditions dans lesquelles il est élaboré [13], mais aussi des propriétés du substrat [14]. La plupart des études montrent que l'orientation (220/204) permet d'obtenir de meilleurs performances photovoltaïques. ...
... Il en résulte une modification de la morphologie de surface du contact arrière. D'après de précédentes études [14][86], cela peut influencer l'orientation cristalline du CIGS déposé sur le contact arrière, ainsi que sur les caractéristiques de l'interface CIGS/Mo. ...
... En effet, la présence de MoSe 2 à l'interface CIGS/Mo est connue pour permettre de former un contact ohmique, évitant la formation d'une barrière Schottky [69]. La dépendance de la formation de cette couche de MoSe 2 envers les propriétés structurelles de la couche de Mo a aussi été démontrée par d'autres groupes [86] [14]. Dans les présents travaux, nous avons montré (figure 4.5) que la morphologie de surface du contact arrière est indirectement affectée par la modification de P A . ...
This PhD work is focused on the development of Cu(In,Ga)Se2 (CIGS) solar cells on metallic substrates. The main goal is to fix various issues related to the replacement of the standard soda-lime glass substrates by metallic substrates (Ti and stainless steel foils), through optimizing and functionalizing of the back contact. Thus, the study is focused on the development of DC-sputtered Mo back contacts. First, monolayer-based and bilayer-based back contacts are compared, demonstrating the interests of the bilayers. The latter are obtained by successively using two different deposition pressures during the DC-sputtering of the back contact. We show that the deposition pressure of the bottom layer of the back contact influences the morphology of the top layer. This leads to changes in the cristallographic properties of the CIGS and in the global device performance. In a second study, the bottom layer is deposited using a Na-doped Mo sputtering target (Mo:Na), in order to use the back contact as a sodium precursor for the CIGS. The differences between the sputtered Mo and Mo:Na layers are first studied. Then, we show that sodium diffusion depends on the deposition pressure of the Mo:Na layer. On Ti substrates, conversion efficiencies as high as on the glass substrates were reached using the Mo:Na layers. It is also shown that when sodium is present, the effect of the deposition pressure of the bottom layer on the device performance is reduced.
... However, all of the previously reported (220/204) oriented films were prepared either by co-evaporation [7][8][9] or molecular beam epitaxy [10] processes. Manipulation of the (220/204) preferred orientation is possible via the influence of the Se activity during film growth [11], change of the substrate type [12], control of the Mo back contact layer properties [13], Na content, and Cu content, as reported [8]. However, we formed a (220/204) preferred orientated CIS film by e-beam treatment without additional selenium in this work. ...
We describe CIS films that are instead deposited by DC and RF magnetron sputtering from binary Cu2Se and In2Se3 target without supply of selenium. Electron beam annealing method as a novel method was used for crystallization of Cu2Se/In2Se3 stacked precursors. The surface, cross-sectional morphology and compositional ratio of CIS films was investigated for the confirmation of the possibility in crystallization without any addition of selenium. Through our works, e-beam annealing method can be a good candidate for rapid crystallization of Cu-In-Se sputtered precursors
... 6 The orientation of the MoSe 2 layer in solar cells plays an important role in determining the orientation of the (In,Ga) 2 Se 3 overlayer and that of the CIGS film. 8,9 It hss been reported that the Mo-Se bond in MoSe 2 sheets is covalent or the bonding between MoSe 2 sheets is van-der-Waals type. ...
Cu(In,Ga)Se-2 (CIGS) solar cells fabricated on soda-lime glass (SLG) exhibited high efficiency due to the supply of Na from the SLG substrate. As a simple doping method, Na can be supplied into CIGS films using a Na compound deposited on Mo electrodes. In this study, the authors compared the properties of CIGS thin films grown on a NaF layer deposited on Mo-coated Na-free glass with those of CIGS films on Mo-coated SLG by a standard through high-resolution transmission electron microscopy and low-temperature photoluminescence analyzes. After NaF deposition on the Mo film, an amorphous interlayer was detected at the CIGS/MoSe2 interface, and the MoSe2 layer that formed on the Mo surface was thin. The photoluminescence study showed that NaF doping did not effectively prevent the formation of deep donors in the CIGS film, whereas Na supplied by SLG effectively prevents their formation. We concluded that the poor performance of CIGS solar cells incorporating a NaF precursor is due to the amorphous layer at the CIGS/Mo interface and different luminescence characteristic with standard CIGS films, resulting in a low minority carrier collection.
... porosity, specific surface area, and fiber diameter). 22,36,37 Therefore, to further improve the accuracy of the model, the key structural properties (e.g., specific surface area, porosity and pore radius) of GFA5 graphite felt used in the experiments were obtained using a suite of validated microstructure characterization algorithms described in the authors' previous work. 22,36,37 To summarize, the electrode material was initially imaged using a SkyScan 1172 X-ray tomograph. ...
... 22,36,37 Therefore, to further improve the accuracy of the model, the key structural properties (e.g., specific surface area, porosity and pore radius) of GFA5 graphite felt used in the experiments were obtained using a suite of validated microstructure characterization algorithms described in the authors' previous work. 22,36,37 To summarize, the electrode material was initially imaged using a SkyScan 1172 X-ray tomograph. A binary segmentation was performed on the resulting tomogram to differentiate the solid and pore phases, and then the tomogram was assembled into a 3D virtual volume. ...
... More detailed information regarding the algorithms can be found in. 22,36,37 These properties were used as input parameters for the electrode domain and are presented in Table III. ...
This paper presents a 2-D transient, isothermal model of a vanadium redox flow battery that can predict the species crossover and related capacity loss during operation. The model incorporates the species transport across the membrane due to convection, diffusion, and migration, and accounts for the transfer of water between the half-cells to capture the change in electrolyte volume. The model also accounts for the side reactions and associated changes in species concentration in each half-cell due to vanadium crossover. A set of boundary conditions based on the conservations of flux and current are incorporated at the electrolyte| membrane interfaces to account for the steep gradients in concentration and potential at these interfaces. In addition, the present model further improves upon the accuracy of existing models by incorporating a more complete version of the Nernst equation, which enables accurate prediction of the cell potential without the use of a fitting voltage. A direct comparison of the model predictions with experimental data shows that the model accurately predicts the measured voltage of a single charge/discharge cycle with an average error of 1.83%, and estimates the capacity loss of a 45 cycle experiment with an average error of 4.2%.
The effect of the substrate temperature during the deposition of a ZnO:Al (AZO) window layer on the performance of Cu(In, Ga)Se2 (CIGS) solar cells was studied. Although the structural, electrical and optical properties of separate AZO films are enhanced with higher substrate temperature, the overall performance of final CIGS solar cells is deteriorated. At higher substrate temperature, the diffusion of Cd, Zn and Al into the CIGS absorber layer was observed with secondary ion-mass spectroscopy measurements. This diffusion could form a buried p–n junction, resulting in deteriorated device characteristics.
