Optimizing Thin-Film Solar Cell Performance: A Comparative Numerical Analysis of GaAsN, GaInAsN and GaInAsNSb-Based Structures Using SCAPS-1D ()
1. Introduction
The necessity of energy is growing continuously for technological and industrial development on a global scale but fossil petroleum like coal, natural gas and oil etc. have a limited supply. On the other hand, serious environmental pollution caused by the ongoing increase in the amount of carbon dioxide (CO2) and other greenhouse gases (GHGs) due to industrialized processes and energy ignition is a stark warning to everyone in the last year [1] [2]. Given these conditions, renewable, green, and clean energy sources have garnered a lot of interest due to their ability to both meet the world’s massive energy demands [3]-[5] and diminish the amount of greenhouse gases in the environment sustainably. Solar energy is regarded as one of the most important renewable and sustainable energy sources for photovoltaic applications [6] [7], such as solar cells, because it is both vast internationally and ecologically favourable. However, the primary disadvantages of solar cells over conventional systems are their higher cost [8] and relative efficiency restrictions. It is predicted that the matters will be resolved as technology progresses. It is usual practice to use a reasonably broad band gap for single junction solar cells, because more than 1.7 eV is not conducive [9]. The Shockley-Queisser (S-Q) numerical computations determine that the maximum efficiency limit for a single junction solar cell is 33.7% [10]. One way to overcome the limitations of single junction solar cells was to use multi-junction solar cells [11]. Higher light conversion efficiencies that are beyond the theoretical S-Q limit are made possible by multi-junction solar cell structure; however, the structure has a problem with structural complexity. In terms of cost/watt ratio [12], lightweight design [13], and flexible manufacturing process [14], a thin-film solar cell is a more affordable choice to gradually find new and varied uses [15]. Significant research may be conducted on this device to improve its performance by fine-tuning its structure, structural parameters, and fabrication materials. This is because the fundamental performance metrics of solar cells, such as J-V characteristics, quantum efficiency (QE), open circuit voltage (
), short circuit current density (
), fill-factor
and efficiency (η), can be accurately controlled by fabrication materials and physical configurations.
Diluted nitrides semiconductors, such as GaAs1−xNx, GaP1−xNx, GayIn1−yAs1−xNx, InP1−xNx and GayIn1−yAs1−x−zNxSbz belong to group III-V compound semiconductors that are created by incorporating a small percentage of N atoms into the host alloys [16] [17]. The electrical, optical, and crystallographic properties of diluted nitrides are greatly influenced by the compositional constituents’ properties and amounts, such as nitrogen’s short atomic radius, high electronegativity, and percentage of concentration etc. [18]-[20]. Among various dilute nitrides semiconductors, GaAs1−xNx, GayIn1−yAs1−xNx, and GayIn1−yAs1−x−zNxSbz have emerged as promising candidates due to their exceptional advantageous electrical and optical properties that make them ideal for innovative next-generation optoelectronics, particularly photovoltaic applications [21]. Several studies on dilute nitrides based solar cells have been reported previously where reported efficiency is much lower than the expected value [22]-[24]. Therefore, to achieve better performance from the devices, the GaAs1−xNx, GayIn1−yAs1−xNx, and GayIn1−yAs1−x−zNxSbz have been considered as absorber layer materials in this research. The study also explores the effects of N, In and Sb atoms on the performance parameters of the proposed solar cell structures.
The first substance, GaAs1−xNx, is a ternary compound creating when nitrogen (N) atoms replace a small percentage of group-V element As-atoms in the host GaAs alloy. Most notably, GaAs’s band-gap reduction takes place via the conduction band as well as lattice constant is drastically lowered by nitrogen atoms [18]. As a result, it possesses abilities to absorb longer-wavelength photons, outstanding absorption coefficients and charge-transport characteristics, which are crucial for high-efficiency solar cells. In addition, this alloy increased photoluminescence (PL) intensity under laser irradiation [25] which is a proof of its dependability and longer operational life. Because of these superior properties, GaAs1−xNx has been considered as first absorber layer’s material of the proposed thin film solar cell structure in this study. The quaternary GayIn1−yAs1−xNx alloy, the second absorber layer material examined in our study, is created when indium (In) atoms are added into GaAs1−xNx alloy to swap out a small percentage of Ga-atom. Because of its special characteristics, GayIn1−yAs1−xNx has been considered a breakthrough material. The In-atom having a higher atomic radius remarkably stretches the lattice structure and band-gap energy. Thus, its lattice parameter can be adjusted for matching with that of either GaAs or Ge for efficient hetero-junction formation and also the band gap energy can be tuned to a suitable value in the optical range, simultaneously by selecting appropriate nitrogen and indium concentrations in this alloy [26] [27]. The introduction of indium further expands the absorption range of GaAsN into the infrared region, allowing GaInAsN cells to absorb photons with wavelengths up to 1100 nm. Thus, it is considered as a candidate for third sub-cell layer in high efficiency multi-junction (MJ) solar cell [28]-[30] and for an active layer substance in high-characteristics-temperatures long-wavelength laser diodes for optical fiber communications [31]-[35]. The adding of antimony (Sb) atoms into GayIn1−yAs1−xNx makes the alloy GayIn1−yAs1−x−zNxSbz. Sb-atom plays a vital part in adjusting the band gap by the alignment of the valance band in this alloy [36]-[38]. In fact, the simultaneous incorporation of N and Sb atoms into GaAs or GaInAs modifies both the conduction and valance bands respectively, thereby creates a scope to enhance photon absorption capability. Nevertheless, the insertion of Sb also dramatically boosts the material’s crystalline and optical qualities [39]. For example, Sb atoms increase photon absorption up to 1300 nm, thereby GayIn1−yAs1−x−zNxSbz is considered as a potential candidate for the next generation high efficiency multi-junction solar cell application [40]. So, this alloy has been regarded as third material for the absorber layer in this study. Along with taking absorber layer materials into consideration, some innovative materials have been used for window layer, electron transport layer (ETL) and hole transport layer (HTL) layer. GaAs has been employed as a window layer in this study due to its less susceptibility to overheating, less noise productivity in electrical circuit, long-time stability and fairly priced [41]. The adding of aluminum (Al) ions into GaAs makes AlGaAs alloy which have been used as ETL and HTL in this study because it’s special optical and electrical characteristics would appropriate for thin-film structure [42] [43]. It is possible to adjust the material’s bandgap by Al-atoms concentration to maximize the cell’s capacity to absorb light. In the meantime, AlGaAs can be used as a surface passivation layer to GaAs solar cells to lower complicated losses and interfacial trap states, boosting the cells’ efficiency and open-circuit voltage [44] [45].
The suggested structures were simulated first by utilizing these materials as discussed above and then the reliance of thicknesses of absorber and buffer layers, doping density of various layers, defect density and temperature on the solar cell’s parameters was examined using SCAPS-1D software. The paper is divided into five sections. Section 1 provides a brief overview of the research that was done for this study. Section 2 will address methods and procedures, including a suggested thin-film solar cell fabrication and modelling strategy. Section 3 displays the analysis of J-V characteristics,
,
,
, η and QE for different properties of fabricating materials as well as physical structure of thin-film solar. Section 4 will provide a succinct conclusion to the findings.
2. Methods and Methodology
A schematic representation of the proposed thin-film solar cell structure n+GaAs/n−AlGaAs/p-absorber layer/p+AlGaAs/p++GaAs is shown in Figure 1. The uppermost n+ type GaAs layer and n− AlGaAs were used as window and ETL respectively. The three novel materials GaAsN, GaInNAs, and GaInNAsSb have been used as absorber layer’s materials individually in this proposed structure, titled Cell 1, Cell 2 and Cell 3 respectively. The essential data of GaAs1−xNx with 1.7% nitrogen concentrations (x = 0.017) [46]; GayIn1−yAs1−xNx with 8% indium and 2.8% nitrogen (y = 0.08 and x = 0.028) [47]; and GayIn1−yAs1−x−zNxSbz with 9% indium, 2.5% nitrogen, and 5.5% antimony (Sb) (y = 0.09, x = 0.025 and z = 0.055) [48] were used in this simulation. The bottom most highly doped p− type GaAs and p+ AlGaAs have been used as window layer and HTL respectively. A depletion layer develops at the pn-junction, which is created by the n− type AlGaAs layer and the p− type absorber layer. The solar cell is exposed to
of sunlight at an operating temperature of
using the global air mass
spectrum. For the suggested solar cell structure, the optimal values for the series (Rs) and shunt (Rsh) resistances have been taken into account. One of the most well-known and trustworthy computer simulation tools, “Solar Cell Capacitance Simulator’s one-dimensional simulation software (SCAPS-1D),” was used to model the suggested structure and examine the performance characteristics. Burgelman et al. from the University of Gent’s Department of Electronics and Information Systems in Belgium developed the program for thin-film solar cells [49]. Solar cell researchers can use this method to efficiently analyse the device structure [50] [51]. Electrical characterisations and spectrum responses of solar cells can be performed with this very helpful tool. The performance characteristics of the solar cell are estimated by the SCAPS-1D program using numerical solutions of the semiconductor continuity equation and Poisson’s equation. For the production of thin-film solar cells, many studies have already confirmed that the real findings and the SCAPS-1D theoretical simulation result are in good agreement.
First of all, we have simulated thin-film solar cells with GaAsN alloys as an absorber layer (Cell 1) and investigate the performance by varying different parameters of the structure. Then, to explore the effects of nitrogen, indium and antimony atoms concentration on the performance parameters, similar measurement was also carried-out for GaInAsN (Cell 2) and GaInAsNSb (Cell 3) alloys. Finally, the obtained results have been compared to get optimum performance. The essential data of materials used for the simulation are shown in Table 1.
Figure 1. Proposed photovoltaic solar cell (PSC) structure.
Table 1. Essential data of materials used for the SCAPS 1D simulation.
Parameters |
p++GaAs/n+GaAs [22] |
GaAsN [22] [52] [53] |
GaInAsN [54]-[56] |
GaInAsNSb [57] |
p+AlGaAs/n−AlGaAs [58]-[60] |
Thickness (nm) |
2/100 |
1000* |
1000* |
1000* |
5* |
Band gap, Eg (eV) |
1.42 |
1.33 |
1.0 |
1.0 |
1.81 |
Electron affinity, χ (eV) |
4.07 |
4.07 |
4.0 |
4.39 |
3.74 |
Dielectric permittivity (relative), ϵt |
12.5 |
12.38 |
10.9 |
12.50 |
12.10 |
CB effective density of states, Nc (
) |
|
|
|
|
|
VB effective density of states, Nv (
) |
|
|
|
|
|
Electron mobility, μn (
) |
|
|
|
|
|
Hole mobility, μp (
) |
|
|
|
|
|
Shallow uniform donor density, ND (
) |
|
0 |
0 |
0 |
|
Shallow uniform acceptor density, NA (
) |
|
|
|
|
|
Type of defect |
Single donor/acceptor |
Single donor |
Single donor |
Single donor |
Single donor/acceptor |
Defect density, Nt |
|
|
|
|
|
Lattice mismatch at the interface between the absorber layer and the window layer were evaluated at the first stage of this study for three absorber layer materials separately because this parameter is a crucial component impacting the structural quality and overall performance of the solar cell. For GaInAsN as an absorber layer material, which includes 8% indium (In) and 2.8% nitrogen (N), the lattice constant is 5.654 Å, resulting in a computed misfit of −0.11% compared to AlGaAs (5.66 Å). This tiny lattice mismatch reflects a very low strain between these two layers, allowing for higher crystal quality and minimum defect development. In the instance of GaInAsNSb, with 9% indium (In), 2.5% nitrogen (N), and 5.5% antimony (Sb), the lattice constant is 5.97 Å, resulting to a more severe positive mismatch of +5.48% with respect to AlGaAs. This bigger mismatch may create strain, which might possibly lead to dislocations but can also enhance material characteristics, such as improved carrier mobility and photon absorption. For GaAsN, with 1.7% nitrogen (N) and a lattice constant of 5.63 Å, the misfit is −0.53% to AlGaAs, showing somewhat higher strain than InGaAsN but still within a reasonable range for retaining acceptable crystal quality. These differences in lattice misfit underline the necessity of exact material composition, notably in the addition of indium, nitrogen, and antimony, to maximize both structural compatibility and higher photovoltaic efficiency.
3. Results and Discussion
According to Figure 1, initially we have simulated the proposed thin-film solar cell structure with GaAsN alloy as an absorber layer and then investigated the performance through varying different parameters of the structure. Then, to explore the effects of nitrogen, indium and antimony atoms concentration on the performance parameters, similar simulation and measurement were also carried-out individually for two other absorber layer materials GaInAsN and GaInAsNSb. Finally, the obtained results have been compared and analyzed.
3.1. J-V Characteristics of Three Dilute Nitride-Based Photovoltaic
Solar Cells—GaAsN, GaInAsN, and GaInAsNSb
First of all, the J-V characteristics of three dilute nitride-based photovoltaic solar cells—GaAsN, GaInAsN, and GaInAsNSb were investigated and then compared as shown in Figure 2 to assess their electrical performance metrics, such as short-circuit current density (Jsc), open-circuit voltage (Voc), and overall efficiency (η).
Figure 2. J-V Characteristics of three dilute nitride-based photovoltaic solar cells—GaAsN, GaInAsN, and GaInAsNSb.
As shown in Figure 2, Cell 1 and Cell 3 exhibited nearly similar J-V characteristics while Cell 2 produced comparatively higher short-circuited current density apart from those. It is also noticed that all the three structures produced approximate same open circuited voltage of 1.04 V. It is seen from Figure 2 that GaAsN-based Cell 1 and GaInAsNSb-based Cell 3 produced Jsc of ~33.8 mA/cm2 and of ~34.8 mA/cm2, respectively while GaInAsN-based Cell 2 produced comparatively higher Jsc of ~46.8 mA/cm2. Thus, the addition of In atoms to GaAsN making GaInAsN is beneficial to be used as absorber layer for improving short circuit current density. Furthermore, the addition of Sb atoms to GaInAsN making GaInAsNSb is not so effective for improving short circuit current density because it showed a balanced performance comparable to GaAsN. The narrower absorption ranges of GaAsN resulting from its greater band-gap restricted its capacity to collect longer-wavelength photons, leading to a lower Jsc. The addition of indium into the GaAsN structure lowered the bandgap, offered lowest lattice mismatch to AlGaAs among the three structures, allowed for improving absorption of near-infrared photons and therefore raised Jsc. GaInAsNSb which combines both indium and antimony in GaAsN attained a performance similar to GaAsN. It seems that the combined effect of In and Sb atoms in GaInAsNSb mitigates the effects of each other so that J-V curves of GaAsN-based Cell 1 and GaInAsNSb-based Cell 3 are mostly similar. Antimony’s addition to the GaInAsN alloy further stretched the energy bands, optical absorption bands and lattice parameter which may have decreased photon consumption over a wider wavelength range for charge carrier formation and, as a result, decreased the alloy’s overall current density in comparison to GaInAsN. Despite the same value of Voc obtained from each cell, the larger value of Jsc leads a greater total power output and efficiency, making Cell 2 the most efficient among the three.
3.2. Absorber Layer’s Thickness Optimization on Photovoltaic (PV)
Parameters
The one of the most crucial factors in improving solar cell performance is the absorber layer’s thickness [61]. The investigations shown in Figures 3(a)-(d) explore the effects of absorber layer’s thickness on the photovoltaic characteristics of the three solar cells, emphasizing differences in Jsc, Voc, FF, and η, respectively. It has been noticed that Jsc of the three designed cells showed increasing tendency with increasing absorber layer’s thickness. However, the value of that parameter for Cell 2 remains relatively in the higher range than other two cells over the whole range of thickness. Cell 1 (GaAsN) displays a continuous increase in Jsc from 31.9 to 34.6 mA/cm2 as thickness climbs to 2.5 µm shown in Figure 3(a), but its Voc stays approximately constant at 1.04 V observed in Figure 3(b), however FF decreases slightly from 87.3% to 85.4% as illustrated in Figure 3(c). Its efficiency peaks at 30.6% at 1.5 µm but saturates subsequently shown in Figure 3(d). Cell 2 (GaInAsN) obtains the maximum performance, with Jsc growing from 44.5 to 48.0 mA/cm2, attributable to improved photon absorption by GaInAsN, while Voc begins at 1.05 V but declines slightly to 1.01 V due to higher recombination in thicker layers. Its FF, ranging from 68.7% to 71.2%, is lower than Cell 1 and Cell 2. However, Cell 2’s efficiency achieves a high of 34.7% at 2.5 µm, powered by GaInAsN’s adjustable band-gap and greater light absorption. Cell 3 (GaInAsNSb) shows Jsc rising from 33.3 to 35.3 mA/cm2, with Voc stabilizing at 1.04 V and FF maintaining high values (86.2% - 86.3%). Efficiency stabilizes about 31.6%, modestly surpassing Cell 1 but falling short of Cell 2. The research reveals that the GaInAsN structure gives the highest performance because to its greater Jsc and efficiency, while the inclusion of antimony in GaInAsNSb increases stability over the whole range of thickness. From this analysis, we suggested fabricating the proposed thin-film solar cell structure with absorber layer’s thickness 1 µm (1000 nm) for obtaining better performances.
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Figure 3. Impact of absorber layer thickness on (a) Jsc (b) Voc (c) FF (d) Efficiency, η of Photovoltaic (PV) solar cells.
3.3. Impact of Thickness of Bottom-Most p++ GaAs Window Layer
on Solar Cell Performance
The section analyzes how increasing the thickness of bottom-most p++ GaAs window layer impacts the performance metrics of GaAsN, GaInAsN, and GaInAsNSb-based solar cells, concentrating on Jsc, Voc, FF, and efficiency as shown in Figures 4(a)-(d) respectively. For the p++ GaAs layer, variations in thickness demonstrate negligible influence on overall performance for all three cells. Cell 1 displays about constant Jsc values at 33.8 mA/cm2 in Figure 4(a) regardless of thickness, demonstrating that differences in the p++ GaAs layer do not substantially impair carrier collection. Similarly, Cell 2 maintains a consistent Jsc of 46.8 mA/cm2 across all thicknesses, suggesting no impact of the layer’s thickness on the GaInAsN structure. For Cell 3, Jsc marginally rises from 34.6 mA/cm2 at 2 nm to 35.5 mA/cm2 at 10 nm before stabilizing, indicating a small enhancement in carrier collection owing to Sb-enhanced passivation in the GaInAsNSb structure. It has been seen from Figure 4(b) that Voc stays consistent at 1.04 V across all thicknesses for the three cells, showing that modifying the p++ GaAs layer thickness does not affect the built-in potential or carrier separation. The FF also stays constant: 86.8% for Cell 1, 69.9% for Cell 2, and 86.3% for Cell 3 as depicted in Figure 4(c), suggesting negligible influence of the p++ GaAs layer thickness on the diode properties. Efficiency shown in Figure 4(d) follows a similar trend: it continues at 30.4% for Cell 1 and 33.9% for Cell 2, while Cell 3 shows a tiny rise from 31.0% at 2 nm to 31.9% at 10 nm. This illustrates the p++ GaAs layer’s principal function as a passivation layer, with negligible impact on carrier transmission or collection. The findings from this section reveal that although the three proposed structures produce similar behavior in all parameters with increasing thickness, but GaInAsN-based structure gives the highest performances. Thus, we proposed the thickness of bottom-most p++ GaAs layer should be minimum as possible around 0.002 µm (2 nm).
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Figure 4. Variation of p++ GaAs thickness on (a) Jsc (b) Voc (c) FF (d) Efficiency, η on Photovoltaic (PV) solar cells.
3.4. Impact of Thickness of Upper-Most n+ GaAs Window Layer on
Solar Cell Performance
In contrast to p++ GaAs layer, difference in the upper-most n+ GaAs layer thickness considerably impacts Jsc and efficiency, notably for Cells 1 and 2 as demonstrated in Figure 5. For Cell 1, Jsc declines drastically from 33.8 mA/cm2 at 0.1 µm to 18.5 mA/cm2 at 1.5 µm, showing greater recombination losses and lower carrier collecting efficiency in thicker layers. Similarly, Cell 2’s Jsc drops from 46.8 mA/cm2 at 0.1 µm to 31.4 mA/cm2 at 1.5 µm.
Figure 5. Variation of n+ GaAs thickness (a) Jsc (b) Voc (c) FF (d) Efficiency, η on Photovoltaic (PV) solar cells.
As seen from the Figure 5(a), Cell 3 demonstrates a minor initial rise in Jsc from 34.6 mA/cm2 at 0.1 µm to 36.6 mA/cm2 at 0.3 µm before falling to 26.6 mA/cm2 at 1.5 µm, indicating excellent carrier transport at intermediate thicknesses and a reduced influence of recombination losses owing to Sb inclusion. Voc stays steady at 1.04 V throughout all thicknesses for Cell 1, but Cell 2 suffers a little decline from 1.04 V to 1.02 V with increasing thickness. Cell 3 exhibits steady Voc values (1.04 V to 1.05 V), further showing Sb’s stabilizing impact as illustrated in Figure 5(b). The FF for Cell 1 rises minimally from 86.8% at 0.1 µm to 87.6% at 1.5 µm, demonstrating moderate sensitivity to n+ GaAs layer thickness. Conversely, Cell 2 exhibits a reduction in FF from 69.9% to 68.9% with increasing thickness, whereas Cell 3 maintains a consistent FF of 86.5% shown in Figure 5(c), indicating Sb’s involvement in regulating electrical characteristics. In Figure 5(d), efficiency patterns parallel those of Jsc: Cell 1’s efficiency lowers dramatically from 30.4% at 0.1 µm to 16.9% at 1.5 µm, while Cell 2’s dips from 33.9% to 23.2%, owing to increasing recombination losses. For Cell 3, efficiency declines more gradually from 31.0% at 0.1 µm to 24.2% at 1.5 µm, illustrating the durability of the GaInAsNSb structure against thickness fluctuations. Considering Jsc, Voc and η, GaInAsN-based structure has been found comparatively better than other two structure. A thickness of around 0.01 µm (100 nm) is advised in this section for the uppermost n+ GaAs layer for getting improved performance.
3.5. Impact of Thickness of p+ AlGaAs HTL on Solar Cells
Performance
Figure 6. Impact of p+ AlGaAs HTL thickness on (a) Jsc (b) Voc (c) FF (d) Efficiency, η on Photovoltaic (PV) solar cells.
For the p+ AlGaAs HTL, the findings showed minor influence on Cells 1 and 2, but Cell 3 benefitted from increased thickness of HTL as illustrated in Figures 6(a)-(d).
As demonstrated in Figure 6(a), Cell 1 retains a consistent Jsc of 33.8 mA/cm2 throughout all thicknesses from 5 nm to 50 nm, suggesting that carrier collecting efficiency is unaltered. Cell 2 exhibits a modest drop in Jsc from 46.8 mA/cm2 at thinner layers to 46.5 mA/cm2 at 50 nm, demonstrating minor effect of the p+ AlGaAs layer thickness on GaInAsN cells. For Cell 3, however, Jsc rises dramatically from 34.6 mA/cm2 at 5 nm to 39.6 mA/cm2 at 50 nm, indicating improved carrier collection owing to Sb inclusion. Voc stays fixed at 1.04 V for all three cells over the full thickness range observed in Figure 6(b), demonstrating that the p+ AlGaAs layer thickness has no influence on the built-in potential or carrier separation. Similarly, FF shown in Figure 6(c) remained stable: 86.8% for Cell 1, 69.9% to 70.5% for Cell 2, and 86.3% for Cell 3, exhibiting negligible susceptibility to thickness fluctuations. Efficiency visualized in Figure 6(d) also stays consistent for Cells 1 and 2, at 30.4% and 33.9%, respectively, while Cell 3 demonstrates a considerable increase from 31.0% at 5 nm to 35.9% at 50 nm, showing Sb’s capacity to boost carrier collection and minimize recombination losses.
3.6. Impact of Thickness of n− AlGaAs ETL on Solar Cell
Performance
Finally, increasing the n− AlGaAs ETL thickness significantly influences Cells 1 and 2 but has negligible effect on Cell 3 as shown in Figures 7(a)-(d), respectively.
For Cell 1, Jsc stays steady at 33.8 mA/cm2 for thin layers (5 - 10 nm) but declines slightly to 33.5 mA/cm2 at 50 nm, suggesting minimal recombination or resistance losses. Similarly, Cell 2’s Jsc declines somewhat from 46.8 mA/cm2 at thinner layers to 46.5 mA/cm2 at 50 nm, but Cell 3’s Jsc stays consistent at roughly 34.6 mA/cm2 across all thicknesses, showing Sb’s function in preserving electron mobility and carrier collection. Voc stays stable at 1.04 V for all three cells, suggesting that n− AlGaAs layer thickness does not alter the voltage characteristics. The FF for Cell 1 reduces considerably from 86.8% at 5 nm to 66.5% at 50 nm, implying higher series resistance with thicker layers. Cell 2’s FF reduces considerably from 73.6% to 68.9%, but Cell 3 maintains a steady FF of 86.3%, further illustrating Sb’s stabilizing impact. Efficiency follows similar trends: Cell 1’s efficiency reduces drastically from 30.4% at 5 nm to 23.1% at 50 nm, while Cell 2’s dips from 33.9% to 33.2%, driven by losses in Jsc and FF. In comparison, Cell 3 demonstrates a small drop in efficiency from 31.0% to 30.3%, showing its robustness to thickness fluctuations due to Sb inclusion. Overall, the findings reinforce the crucial significance of thickness optimization in minimizing recombination losses and boosting carrier transport for Cells 1 and 2, whereas Cell 3’s performance stability across changing thicknesses shows the benefits of Sb inclusion in the GaInAsNSb structure.
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Figure 7. Variation of n− AlGaAs thickness on (a) Jsc (b) Voc (c) FF (d) Efficiency, η on Photovoltaic (PV) solar cells.
3.7. Effect of P-Type Absorber Layer’s Acceptor Doping Density on
PV Parameters
The performance metrics like Jsc, Voc, FF, and η of the three solar cell models in Figure 1 are greatly impacted by acceptor density, as indicated in Figures 8(a)-(d), respectively.
For Cell 1, Jsc shown in Figure 8(a) initially rises from 32.1 mA/cm2 at 1 × 10 15cm−3 to 33.8 mA/cm2 at 1 × 10 18 cm−3 but drops dramatically at higher densities owing to recombination, reaching 22.6 mA/cm2 at 1 × 1020 cm−3. Voc follows a similar tendency, peaking at 1.04 V with moderate doping before significantly declining as seen from Figure 8(b). FF increases to 86.8% at 1 × 10 18 cm−3 but plummets to 68.5% at high doping levels, with efficiency peaking at 30.4% before decreasing to 17.9%. For Cell 2, Jsc demonstrates a substantial spike from 33.2 mA/cm2 to 46.8 mA/cm2 at 1 × 10 18 cm−3, due to GaInAsN’s higher absorption capabilities, while Voc grows gradually from 0.916 V to 1.09 V, suggesting effective carrier separation. FF peaks at 76.0% at 1 × 1019 cm−3, with efficiency reaching an amazing 38.7%. Cell 3, adding Sb, maintains consistency across all measures, with Jsc and Voc being steady at 34.6 mA/cm2 and 1.04 V, respectively, and FF at 86.3%, resulting in stable efficiency around 31%. These trends demonstrate that Cell 2 excels in efficiency (38.7%) owing to improved band-gaps and absorption, whereas Cell 3 provides higher stability under variable doping concentrations. Cell 1, while effective at modest doping levels, experiences large losses at greater densities owing to recombination. This research underlines the trade-offs between performance optimization and stability among the cells. Our proposed solar panel’s absorber layer should have an acceptor doping density of 1 × 1016 cm−3.
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Figure 8. Variation of absorber layer acceptor density on (a) Jsc (b) Voc (c) FF (d) Efficiency, η on Photovoltaic (PV) solar cells.
3.8. Influence of n+ GaAs Layer’s Donor Doping Density on PV
Parameters
The performance of the proposed solar cells is greatly impacted by differences in doping concentrations in various layers, notably the n+ GaAs, p+ AlGaAs, and n− AlGaAs layers. In all designed three cell types, the donor density of the n+ GaAs layer has a considerable influence on the cell’s photovoltaic (PV) properties, including Jsc, Voc, FF, and η as illustrated in Figures 9(a)-(d), respectively.
Figure 9. Variation of n+ GaAs donor density on (a) Jsc (b) Voc (c) FF (d) Efficiency,
on Photovoltaic (PV) solar cells.
For Cell 1, increasing the donor density of the n+ GaAs layer leads in a constant increase in Jsc, from 28.7 mA/cm2 at 1 × 1015 cm−3 to 33.5 mA/cm2 at 1 × 1019 cm−3 as seen from Figure 9(a). This is followed by a considerable improvement in Voc of Figure 9(b), which jumps from 0.84 V to 1.09 V, suggesting improved band alignment and less recombination losses. The fill factor shown in Figure 9(c) also rises from 59% to 87.4%, adding to a boost in efficiency from 14.2% to 31.9% as illustrated in Figure 9(d). This improvement is possibly due to the decreased series resistance and better carrier transport associated with increased doping densities. In Cell 2, the Jsc rises from 46.2 mA/cm2 at 1 × 1015 cm−3 to 47.2 mA/cm2 at 1 × 1017 cm−3, but reduces at higher doping levels because to increased recombination, revealing a balance between greater carrier collection and recombination. Voc stays steady at 1.04 V throughout doping densities, whereas FF grows from 58.2% to 69.9%, culminating at moderate doping levels, with efficiency rising from 27.8% to 33.9%. In Cell 3, the Jsc climbs gradually from 33.4 mA/cm2 at low doping densities to 36.8 mA/cm2 at 1 × 1019 cm−3, boosted by the addition of Sb, which helps retain favorable electron transport and minimize recombination. The Voc rises from 0.855 V to 1.10 V, while FF stays consistent at 86%, suggesting that Sb stabilizes the electrical properties. Efficiency climbs from 24.6% to 33.8%, illustrating the value of Sb in sustaining high performance over a wide range of doping concentrations. The higher values of Jsc and efficiency making Cell 2 the most efficient among the proposed three structures. For improved performance, doping the n+ GaAs layer with an impurity density of 1 × 1017 cm−3 is advised.
3.9. Influence of p+ AlGaAs HTL’s Acceptor Doping Density on PV
Parameters
Figure 10. Impact of p+ AlGaAs density on (a) Jsc, (b) Voc (c) FF and (d) Efficiency, η on Photovoltaic (PV) solar cells.
Regarding the p+ AlGaAs layer shown in Figure 10, Cell 1 displays minor changes in Jsc, Voc, and efficiency with varied doping densities, demonstrating that p+ AlGaAs doping does not substantially alter the cell’s performance. Similarly, Cell 2 demonstrates consistent performance at lower doping levels, with a modest reduction in Voc at high doping densities, whereas FF improves from 56.0% to 69.9% as doping density grows, leading to a steady efficiency gain from 27.6% to 33.9%. In Cell 3, efficiency climbs slightly from 28.9% to 31.0% as doping increases, demonstrating that the p+ AlGaAs doping impacts efficiency but with declining returns compared to the n+ GaAs layer.
3.10. Influence of n− AlGaAs ETL’s Donor Doping Density on PV
Parameters
The doping density in the n− AlGaAs ETL layer has a more substantial influence on the performance of the solar cells as illustrated in Figure 11. For Cell 1, the Jsc remains approximately constant at 34.5 mA/cm2 up to doping density level 1 × 1018 cm−3 but declines rapidly at 1 × 1019 cm−3 as seen from Figure 11(a) for GaAsN. Similarly, for adding In-atoms, Cell 2 exhibits comparatively higher Jsc which declines from 46.8 mA/cm2 to 33.3 mA/cm2 after decreasing the doping density from 1 × 1018 cm−3 to 1 × 1019 cm−3, attributable to lower electron mobility at higher doping levels. In contrast, Cell 3 displays a rise in Jsc from lower doping densities to 36.4 mA/cm2 at 1 × 1019 cm−3, helped by Sb, which helps maintain excellent carrier transport despite higher doping. It is observed from Figure 11(b) that Voc for Cell 1 climbs from 1.04 V to 1.08 V at high doping densities, showing enhanced carrier separation, whereas Cell 2 and Cell 3 exhibit steady Voc throughout doping densities, proving their tolerance to changes in donor density. The FF shown in Figure 11(c) for Cell 1 reduces rapidly from 87.5% to 71.2% at high doping levels, whereas Cell 2 and Cell 3 also see a fall in FF, albeit less so in Cell 3, where Sb helps preserve stability. The behavior of the
is possibly dependent on the combined behavior of
and
[62] [63]. As demonstrated in Figure 11(d), efficiency in Cell 1 declines from 30.6% to 20.5% at large donor densities, reflecting the reduced Jsc and FF. Cell 2’s efficiency reduces from 34.2% to 29.8%, whereas Cell 3’s efficiency climbs somewhat, reaching 32.6% at 1 × 1019 cm−3. The value of η reflects the total behavior of
,
and
. The presence of Sb in Cell 3 mitigates the deleterious impacts of higher donor density, resulting to more consistent and better performance across all doping levels. Overall, the findings emphasize that while doping density in the n+ GaAs and n− AlGaAs layers significantly influences the efficiency and stability of the solar cells, the incorporation of Sb in the GaInAsN-based cells offers superior performance, particularly in maintaining stable electrical characteristics and achieving high efficiency at a wide range of doping densities. This suggests that careful optimization of doping densities, particularly in the n+ GaAs and n− AlGaAs layers is critical for maximizing the performance of GaAsN and GaInAsN-based solar cells. It is also clarified that Sb plays a crucial role in improving their stability and efficiency across varying doping conditions. For n− AlGaAs ETL, we suggested maintaining a donor doping density level of 1 × 1016 cm−3 in order to get improved performance.
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Figure 11. Impacts of n− AlGaAs donor density on (a) Jsc (b) Voc (c) FF (d) Efficiency,
on Photovoltaic (PV) solar cells.
3.11. Impact of Temperature on the Performance Parameters of
the Solar Cells
Operating temperature has a vital impact on the solar cells performances [64]. In this section, the temperature was changed from
to
to take into account the influence of the working temperature on
,
,
and η performances of dilute nitrides GaAsN, GaInAsN, and GaInAsNSb-based thin-film solar cells which have been illustrated in Figure 12.
As clarified in Figure 12, the performances of these three solar cell structures were greatly impacted by temperature changes. It is noticed for Figure 12(b) that as the temperature rises, Voc drops distinctly for every material used in absorber layer. The reasons are that higher temperature shifts the band gap energy of the dilute nitrides to lower energy [65] and also simultaneously increases the velocity-instability of charged particles [66], reverse saturation current and resistivity of the materials as well. As a result, the probability of recombination rate of charge carriers before reaching the depletion region promotes and eventually degradation of
occurs. Cell 1 (GaAsN) displays nearly stable Jsc and FF shown in Figure 12(a) and Figure 12(c) respectively but suffers a decline in Voc and efficiency with increasing temperature as shown in Figure 12(d). The value of
can be restricted by the device ohmic losses such as series and shunt resistances, metal contact and recombination losses. The constant current density with increasing temperature apparently indicates that the combined effects of these mentioned parameters might mitigate the variation in
of GaAsN-based solar cell in our simulation. The behavior of the
is possibly dependent on the combined behavior of
and
[62] [63]. Constant
and decrement in
jointly led to a decrease in
of the device in Cell 1. Cell 2 (GaInAsN) exhibits nearly constant but large Jsc as well as efficiency with increasing temperature. Cell 3 (GaInAsNSb) gains the considerable rise in Jsc and efficiency with increasing temperature. The value of η reflects the total behavior of
,
and
[67]. Increment in
in large scale with small decrement in both
and
jointly leads the way to increase in the η of the Cell 3. Overall, although all three cells’s Voc drops with increased temperature, Cell 2 displays the largest overall performance, suggesting that GaInAsN is suitable for high-temperature settings, followed by GaInAsNSb, and GaAsN. In order to achieve better results, we also came to the conclusion that thin-film solar cells should be operated at 295 K.
![]()
Figure 12. Effects of temperature on (a) Jsc (b) Voc (c) FF (d) Efficiency, η in thin-film solar cells.
3.12. Quantum Efficiency (QE) of the Proposed Solar Cells
The quantum efficiency (QE) of the proposed GaAsN, GaInAsN, and GaInAsNSb-based thin-film solar cells structures as a function of wavelength has been demonstrated in Figure 13.
Figure 13. QE of the proposed solar cell structures as a function of wavelength.
It can be seen from that figure, Cell 1 (GaAsN) performs well in the visible and near-infrared regions (300 - 900 nm) of the incident light but abruptly loses efficiency in the infrared owing to its band-gap restrictions. On the other hand, Cell 2 (GaInAsN) beats Cell 1, with higher QE in the mid- to long-wavelength regions (400 - 1230 nm) notably in the near-infrared, due to the introduction of indium, which broadens the absorption spectrum. Cell 3 (GaInAsNSb) demonstrates the overall QE throughout a larger range, from 300 to 1230 nm, with the inclusion of both indium and antimony boosting absorption, lowering recombination, and prolonging photon capture. By making comparison among the three cells shown in Figure 13, it has been concluded that Cell 2 is the most effective at absorbing photons throughout both visible and infrared light, followed by Cell 3, whereas Cell 1 is confined to shorter wavelengths.
4. Conclusion
This study presents a comparative examination of thin-film solar cells containing GaAsN (Cell 1), GaInAsN (Cell 2), and GaInAsNSb (Cell 3) individually as absorber layer’s material, modeled using SCAPS-1D. The data revealed that material composition, absorber and other layer’s thickness, doping densities, and ambient temperature greatly influence the photovoltaic performance metrics, such as Jsc, Voc, FF, efficiency and QE. Among the three structures, Cell 2 (GaInAsN) resulted as the ideal choice, achieving the maximum efficiency (34.7%) and short-circuit current density (46.8 mA/cm2). Cell 2 also demonstrated better quantum efficiency across the visible and near-infrared wavelengths, making it suited for high-performance photovoltaic applications. Additionally, it maintained robust performance throughout a wide range of absorber thicknesses, doping concentrations, and operating temperatures, proving its versatility and efficiency in varied settings. Cell 3 (GaInAsNSb) displayed an increased absorption range up to 1300 nm, owing to antimony inclusion, which improved carrier collection, reduced recombination losses, and enhanced stability. While its efficiency (31.6%) fell short of Cell 2, its steady performance under varied climatic and structural circumstances makes it a suitable contender for applications needing greater reliability. Cell 1 (GaAsN), while demonstrating acceptable performance metrics, was limited by its smaller absorption range and lower Jsc (33.8 mA/cm2), resulting in a peak efficiency of 30.6%. This underlines the necessity for compositional adjustments, such as the incorporation of indium or antimony, to improve its performance. Overall, the work emphasizes the remarkable performance of GaInAsN for thin-film solar cells, combining high efficiency, excellent quantum efficiency, and adaptability. GaInAsNSb, with its increased stability and expanded absorption range, has promise for specialized applications. These findings would open the new door for further experimental study to optimize dilute nitride-based solar cells performance for next-generation photovoltaic technology.
Funding
The research works have been conducted by self-fund.
Data Availability Statement
The data of this study are available from the corresponding author upon reasonable request.
Acknowledgements
The authors would like to thank Marc Burgelman, Department of Electronics and Information System, University of Gent, Belgium for allowing the opportunity to use SCAPS-1D for simulation. They are also grateful to the Department of Electrical and Electronic Engineering, Hajee Mohammad Danesh Science and Technology University, Dinajpur-5200, Bangladesh for providing necessary technical supports.