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Lead halide hybrid solar cells have demonstrated exceptional performance in recent years, but concerns over their toxicity and instability have spurred the development of perovskite-based cells without lead. This work explores a lead-free perovskite material consisting of cesium tin-germanium triiodide solid solution perovskite (CsSn0.5Ge0.5I3) is utilized to fabricate solar cells with varying thicknesses and donor densities of the absorber layer. The results imply that enhancing the thickness of the layer boosts the power conversion efficiency (PCE) by facilitating better photon absorption. However, this increase in thickness also causes a reduction in both the open-circuit voltage (VOC) and fill factor (FF). In other words, while thickening the layer improves PCE through increased photon absorption, it also negatively impacts other key performance metrics, such as VOC and FF. Conversely, the effect of donor density (Nd) on the cell's performance is less significant than the CsSn0.5Ge0.5I3 layer's thickness. This study sheds light on the critical role of thickness and donor density in optimizing the performance of CsSn0.5Ge0.5I3-based solar cells. The performance of c-Si and CIGS-based single junction bottom cells under standalone conditions is also analyzed using JV and EQE curves. The C-Si-based single junction solar cell exhibited greater efficiency (21.28%) in converting photons of different wavelengths into electrons compared to the CIGS-based solar cell (16.26%). Lastly, for increasing the PCE of the single-junction solar cells the study moves towards multi-junction solar cells. In this context, two highly efficient TSCs (LFPVK/c-Si and LFPVK/CIGS) are designed and analyzed using the current matching technique, which involves the series connection of the top and bottom cells with increased PV parameters (LFPVK/c-Si-JSC: 21.44 mA/cm2, VOC: 1.45 V, FF: 82.17%, PCE: 25.54% and LFPVK/CIGS-JSC: 21.83 mA/cm2, VOC: 1.33 V, FF: 73.34%, PCE: 21.45%). [ABSTRACT FROM AUTHOR]

Currently, all‐perovskite tandem solar cells have achieved power conversion efficiencies exceeding 29%. The further improvement is limited by mixed Sn–Pb narrow‐bandgap perovskite subcells. The facile oxidation of Sn2+ to Sn4+ poses an inherent challenge that limits the efficiency and stability of Sn–Pb perovskite solar cells. In this study, a multi‐dentate chelating additive, 3‐amino‐2‐chloroisonicotinamide (ACPC), is developed. Its amino group could anchor I− of the perovskite lattice by hydrogen bonds, thereby preventing I− migration and oxidation. On the other hand, the carbonyl group of ACPC as a Lewis base group could coordinate with Sn2+, effectively protecting Sn2+ from oxidation. Ultimately, the multi‐dentate chelating effect of ACPC helps to suppress the oxidation of Sn–Pb perovskite and its related nonradiative recombination. The resulting Sn–Pb perovskite solar cells obtain a top power‐conversion efficiency (PCE) of 23.09% and a high open‐circuit voltage (VOC) of 0.902 V while the control values only reach 19.11% and 0.825 V. As a result of the improved performance of the Sn–Pb perovskite solar cells, the corresponding all‐perovskite tandem solar cells achieve a PCE of 27.60%, retaining 85.7% of initial PCE after 500 h continuous 1 sun illumination. [ABSTRACT FROM AUTHOR]

Tandem solar cells have the potential to be more efficient than the Shockley–Queisser limit imposed on single junction cells. In this study, optical and electrical modeling based on experimental data were used to investigate the possibility of boosting the performance of kesterite/c-Si tandem solar cells by inserting an alternative nontoxic TiO2 buffer layer into the kesterite top subcell. First, with SCAPS-1D simulation, we determined the data reported for the best kesterite (CZTS (Eg = 1.5 eV)) device in the experiments to be used as a simulation baseline. After obtaining metric parameters close to those reported, the influence on the optoelectronic characteristics of replacing CdS with a TiO2 buffer layer was studied and analyzed. Different top subcell absorbers (CZTS0.8Se0.2 (Eg = 1.4 eV), CZTS (Eg = 1.5 eV), CZTS (Eg = 1.6 eV), and CZT0.6Ge0.4S (Eg = 1.7 eV)) with different thicknesses were investigated under AM1.5 illumination. Then, to achieve current matching conditions, the c-Si bottom subcell, with an efficiency at the level of commercially available subcells (19%), was simulated using various top subcells transmitting light calculated using the transfer matrix method (TMM) for optical modeling. Adding TiO2 significantly enhanced the electrical and optical performance of the kesterite top subcell due to the decrease in parasitic light absorption and heterojunction interface recombination. The best tandem device with a TiO2 buffer layer for the top subcell with an optimum bandgap equal to 1.7 eV (CZT0.6Ge0.4S4) and a thickness of 0.8 µm achieved an efficiency of approximately 20%. These findings revealed that using a TiO2 buffer layer is a promising way to improve the performance of kesterite/Si tandem solar cells in the future. However, important optical and electrical breakthroughs are needed to make kesterite materials viable for tandem applications. [ABSTRACT FROM AUTHOR]

The performance of perovskite solar cells (PSCs) is often constrained by significant open‐circuit voltage (VOC) losses attributed to non‐radiative recombination processes induced by detrimental trap states. Surface treatments using passivating ligands typically involve single active binding sites on perovskite, posing challenges for effective passivation. Here, an aromatic donor‐acceptor (D‐A) configured phthalocyanine treatment is proposed to aim at dual‐site passivation of uncoordinated lead ions and effective mitigation of shallow and deep‐level defects on the perovskite surface. The resulting benign p‐type surface facilitates a more favorable energy level alignment and reduces energetic mismatches at the perovskite/Spiro‐OMeTAD interface. Pc‐BTBC, with its aromatic D‐A configuration, demonstrated compatibility with various perovskite compositions. Optimized PSCs achieves a power conversion efficiency (PCE) of 25.15% and reduces the VOC deficit to 0.379 V. Furthermore, encapsulated devices exhibited enhanced stability under damp‐heat conditions (ISOS‐D‐2, 50% RH, 65°C) with a T92 of 1000 h and maintained maximum power point tracking under continuous light in ambient air at 65°C (ISOS‐L‐2). Notably, fabricated wide‐bandgap semitransparent PSCs (ST‐PSCs) achieved a PCE of 20.29%, while four‐terminal perovskite/silicon tandem solar cells (4T‐P/STSCs) demonstrated an efficiency of 29.38%. This study provides insights into minimizing VOC losses and represents significant progress toward commercializing perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

Wide-bandgap (WBG) perovskite has demonstrated great potential in perovskite-based tandem solar cells. The power conversion efficiency (PCE) of such devices has surpassed 34%, signifying a new era for renewable energy development. However, the ion migration reduces the stability and hinders the commercialization, which is yet to be resolved despite many attempts. A big step forward has now been achieved by the simulation method. The detailed thermodynamics and kinetics of the migration process have been revealed for the first time. The stability has been enhanced by more than 100% via the heterojunction layer on top of the WBG perovskite film, which provided extra bonding for kinetic protection. Hopefully, these discoveries will open a new gate for WBG perovskite research and accelerate the application of perovskite-based tandem solar cells. [ABSTRACT FROM AUTHOR]

This research explores the pivotal domain of hydrogen production through photocatalytic processes, providing insights into its potential as a sustainable energy source. In the initial section, the role of hydrogen as a versatile energy carrier is discussed, emphasizing its importance in meeting the world's energy needs. An extensive overview of current hydrogen production methods is provided, emphasizing their limitations. The research also highlights the significance of photocatalytic semiconductor materials and tandem cell configurations, pointing towards innovative approaches for enhancing hydrogen production. The core of this research involves a comprehensive literature review. It delves into the theory of water-splitting, elucidating the principles of photocatalytic water-splitting within photoelectrochemical (PEC) cells. The application of photocatalysis for water-splitting is examined, along with a deep dive into the factors that influence this process. These factors include the recombination of photogenerated charge carriers, the mechanisms underlying photoanode instability, and the substantial impact of photocurrent density on hydrogen production efficiency. In addition, the integration of Dye-Sensitized Solar Cells (DSSC) as an auxiliary technology is also being explored. By addressing the limitations of current hydrogen production methods and providing a comprehensive overview of photocatalytic processes, this work lays the foundation for further advancements in sustainable energy production. The findings open doors to innovative research, offering pathways to overcome challenges and optimize hydrogen production through photocatalysis for a greener and more sustainable future. In conclusion, this research unearths the potential for clean hydrogen production and renewable energy solutions. • Emphasizing the significance of hydrogen as an energy carrier and the diverse methods used to produce it. • Delves into the subject of photocatalytic semiconductor materials and tandem cells, illustrating their roles in hydrogen production. • Encompassing hydrogen production methods, the theoretical and principles of photocatalytic water splitting, and the utilization of TiO 2 photocatalysts in PEC cells. • Explore the integration of Dye Solar Cell (DSC) to act as an additional layer in the photovoltaic system. [ABSTRACT FROM AUTHOR]

Numerous researchers have dedicated efforts toward enhancing the efficiency of solar cells, particularly through the utilization of multi-junction or tandem solar cell configurations. However, a common approach employed by many researchers involves the use of the standard absorption formula (SAF) to determine the transmitted spectrum from the top cell to illuminate the bottom cells. The SAF method relies on conventional absorption calculations, neglecting reflection, refraction, and parasitic absorption losses. In this study, the transfer matrix (TRM) method, which accounts for reflection and refraction losses and an interference effect, is reported for the accurate calculation of a filtered spectrum. A comparative analysis between the SAF and TRM approaches reveal that the TRM technique provides a more accurate representation of the transmitted spectrum, particularly when considering reflection, refraction, and parasitic absorption losses. The primary aim of this research is to precisely predict the efficiency of tandem configurations by integrating multiple low-bandgap semiconductor bottom cells (BCs) with a top cell (TC) based on high-bandgap perovskite (PVK). Furthermore, the optimization of current matching is achieved by adjusting the thicknesses of the top absorber layer (TAL) and bottom absorber layer (BAL) based on the obtained filtered spectra. Tandem devices optimized using the TRM approach exhibit superior performance, achieving efficiencies of 28.72% (PVK/c-Si), 27.88% (PVK/CIGS), and 29.99% (PVK/PVK). This comparative investigation underscores the importance of considering reflection and refraction losses in tandem solar cell design and highlights the effectiveness of the TRM technique in enhancing device performance. [ABSTRACT FROM AUTHOR]

In order to surmount the Shockley–Queisser efficiency barrier of single-junction solar devices, tandem solar cells (TSCs) have shown a potential solution. Organic and Si materials can be promising candidates for the front and rear cells in TSCs due to their non-toxicity, cost-effectiveness, and possible complementary bandgap properties. This study researches a flexible two-terminal (2-T) organic/Si TSC through TCAD simulation. In the proposed configuration, the organic solar cell (OSC), with a photoactive optical bandgap of 1.78 eV, serves as the front cell, while the rear cell comprises a Si cell based on a thin 70 μm wafer, with a bandgap energy of 1.12 eV. The individual standalone front and bottom cells, upon calibration, demonstrate power conversion efficiencies (PCEs) of 11.11% and 22.69%, respectively. When integrated into a 2-T organic/Si monolithic TSC, the resultant tandem cell achieves a PCE of 20.03%, indicating the need for optimization of the top organic cell to beat the efficiency of the bottom Si cell. To enhance the performance of the OSC, some design ideas are presented. Firstly, the OSC is designed by omitting the organic hole transport layer (HTL). Consequently, through engineering the front contact work function, the PCE is enhanced. Moreover, the influence of varying the absorber defect density of the top cell on TSC performance is investigated. Reduced defect density led to an overall efficiency improvement of the tandem cell to 23.27%. Additionally, the effects of the variation of the absorber thicknesses of the top and rear cells on TSC performance metrics are explored. With the matching condition design, the tandem efficiency is enhanced to 27.60%, with VOC = 1.81 V and JSC = 19.28 mA/cm2. The presented simulation results intimate that the OSC/Si tandem design can find applications in wearable electronics due to their flexibility, environmentally friendly design, and high efficiency. [ABSTRACT FROM AUTHOR]

Abstract Tandem solar cells owing to their layered structure in which each sub-cell utilizes a certain part of the solar spectrum with reduced thermal losses, are promising applicants to promote the power conversion efficiency beyond the Shockley–Queisser limit of single-junction solar cells. This study delves into the performance and optimization of 4-terminal organic/silicon tandem solar cells through numerical simulations using SCAPS-1D software. The tandem architecture combining organic, perovskite, and silicon materials, shows potential in enhancing light absorption across the solar spectrum with complementary absorption spectra. Through innovative material exploration, optimization techniques are explored to advance the performance boundaries of organic/silicon tandem solar cells. The study employs the Beer–Lambert law to assess the impact of varied physical parameters on tandem solar cell efficiency, aiming to propose optimal configurations. Results indicate a maximum efficiency of 25.86% with P3HT:PC70BM organic active layer (150 nm thickness) and 36.8% with Cs2AgBi0.75Sb0.25Br6 active layer (400 nm thickness) in the studied 4-terminal tandem structures. These findings offer valuable insights into the complex physics of these tandem solar cells, for developing high-performance and commercially practical photovoltaic devices.

This study examined the impact of temperature optimization on indium tin oxide (ITO) films in monolithic HJT/perovskite tandem solar cells. ITO films were deposited using magnetron sputtering at temperatures ranging from room temperature (25 °C) to 250 °C. The sputtering target was ITO, with a mass ratio of In2O3 to SnO2 of 90% to 10%. The effects of temperature on the ITO film were analyzed using X-ray diffraction (XRD), spectroscopic ellipsometry, and sheet resistance measurements. Results showed that all ITO films exhibited a polycrystalline morphology, with diffraction peaks corresponding to planes (211), (222), (400), (440), and (622), indicating a cubic bixbyite crystal structure. The light transmittance exceeded 80%, and the sheet resistance was 75.1 Ω/sq for ITO deposited at 200 °C. The optical bandgap of deposited ITO films ranged between 3.90 eV and 3.93 eV. Structural and morphological characterization of the perovskite solar cell was performed using XRD and FE-SEM. Tandem solar cell performance was evaluated by analyzing current density-voltage characteristics under simulated sunlight. By optimizing the ITO deposition temperature, the tandem cell achieved a power conversion efficiency (PCE) of 16.74%, resulting in enhanced tandem cell efficiency. [ABSTRACT FROM AUTHOR]

Double-junction tandem solar cells (TSCs), featuring a wide-bandgap top cell (TC) and narrow-bandgap bottom cell (BC), outperform single-junction photovoltaics, demanding meticulous subcell selection and optimization. Lead-free double perovskites offer sustainable photovoltaic solutions and are less toxic with enhanced stability, versatile compositions, and favorable optoelectronic characteristics. This study investigates the design and performance of a lead-free all-double-perovskite tandem solar cell (DPTSC), utilizing Cs 2 AgBiBr 6 (CABB) with a bandgap of 2.05 eV and Cs 4 CuSb 2 Cl 12 (CCSC) with a bandgap 1.6 eV as absorbers in the TC and BC, respectively. The TC and BC were individually simulated and calibrated against experimental data, forming the basis for tandem device design and optimization. Series and shunt resistance, along with temperature effects on their performance, were examined. Meticulous adjustment of absorber thicknesses achieved optimal current matching between subcells. This fine-tuning closely matches TC current under AM 1.5G spectrum with BC current under a filtered spectrum. At optimal current matching (absorber thickness: 0.365 µm for the TC and 1.4 µm for BC), the DPTSC exhibits impressive power conversion efficiency (PCE) of 28.08% (with V oc = 2.47 V, J sc = 12.78 mA / cm 2 , FF = 88.95%). The external quantum efficiency (EQE), Mott–Schottky and carrier generation/recombination profiles under current matching conditions have also been acquired to provide comprehensive device design insights. The designed TSC shows improved stability against temperature variations. These findings highlight the potential for lead-free and stable double perovskites to serve as subcell absorbers, enabling highly efficient, commercially viable, nontoxic, and eco-friendly tandem photovoltaic technologies. This work contributes valuable insights for advancing TSC technology, supported by comparisons with existing simulated and experimental data. [ABSTRACT FROM AUTHOR]

Tandem solar cells owing to their layered structure in which each sub-cell utilizes a certain part of the solar spectrum with reduced thermal losses, are promising applicants to promote the power conversion efficiency beyond the Shockley–Queisser limit of single-junction solar cells. This study delves into the performance and optimization of 4-terminal organic/silicon tandem solar cells through numerical simulations using SCAPS-1D software. The tandem architecture combining organic, perovskite, and silicon materials, shows potential in enhancing light absorption across the solar spectrum with complementary absorption spectra. Through innovative material exploration, optimization techniques are explored to advance the performance boundaries of organic/silicon tandem solar cells. The study employs the Beer–Lambert law to assess the impact of varied physical parameters on tandem solar cell efficiency, aiming to propose optimal configurations. Results indicate a maximum efficiency of 25.86% with P3HT:PC70BM organic active layer (150 nm thickness) and 36.8% with Cs2AgBi0.75Sb0.25Br6 active layer (400 nm thickness) in the studied 4-terminal tandem structures. These findings offer valuable insights into the complex physics of these tandem solar cells, for developing high-performance and commercially practical photovoltaic devices. [ABSTRACT FROM AUTHOR]

Tunnel oxide passivated contact (TOPCon) silicon solar cells have been developed and transferred into industrial mass production, which is beneficial to the future production of perovskite/silicon tandem solar cells (TSCs) in a large scale. However, the doped polycrystalline silicon (poly‐Si) layer in the poly‐Si‐based passivating contact structure yields a profound optical loss from reflection and parasitic absorption, which obstacles the efficiency promotion of TSCs. In this work, the optical property of poly‐Si is improved by in‐situ oxygen incorporation using plasma enhanced chemical vapor deposition (PECVD) with nitrous oxide (N2O) as the oxygen source. The p‐type oxygen‐incorporated poly‐Si (poly‐SiOx) shows a reduced refractive index and extinction coefficient over 700–1200 nm wavelength, leading to a reduced reflection, a lower parasitic absorption and a higher transmission. After applying an optimized p‐type oxygen‐incorporated poly‐Si in the front‐side poly‐Si passivating contact structure of c‐Si bottom cell, the short‐circuit current density and efficiency of a perovskite/c‐Si tandem cell increases by ≈0.32 mA cm−2 and ≈0.8%, respectively, leading to 25.12% tandem cell efficiency. [ABSTRACT FROM AUTHOR]

Tandem solar cells have the potential to be more efficient than the Shockley–Queisser limit imposed on single junction cells. In this study, optical and electrical modeling based on experimental data were used to investigate the possibility of boosting the performance of kesterite/c-Si tandem solar cells by inserting an alternative nontoxic TiO2 buffer layer into the kesterite top subcell. First, with SCAPS-1D simulation, we determined the data reported for the best kesterite (CZTS (Eg = 1.5 eV)) device in the experiments to be used as a simulation baseline. After obtaining metric parameters close to those reported, the influence on the optoelectronic characteristics of replacing CdS with a TiO2 buffer layer was studied and analyzed. Different top subcell absorbers (CZTS0.8Se0.2 (Eg = 1.4 eV), CZTS (Eg = 1.5 eV), CZTS (Eg = 1.6 eV), and CZT0.6Ge0.4S (Eg = 1.7 eV)) with different thicknesses were investigated under AM1.5 illumination. Then, to achieve current matching conditions, the c-Si bottom subcell, with an efficiency at the level of commercially available subcells (19%), was simulated using various top subcells transmitting light calculated using the transfer matrix method (TMM) for optical modeling. Adding TiO2 significantly enhanced the electrical and optical performance of the kesterite top subcell due to the decrease in parasitic light absorption and heterojunction interface recombination. The best tandem device with a TiO2 buffer layer for the top subcell with an optimum bandgap equal to 1.7 eV (CZT0.6Ge0.4S4) and a thickness of 0.8 µm achieved an efficiency of approximately 20%. These findings revealed that using a TiO2 buffer layer is a promising way to improve the performance of kesterite/Si tandem solar cells in the future. However, important optical and electrical breakthroughs are needed to make kesterite materials viable for tandem applications.

In order to increase the photocurrent of tandem solar cells with a silicon (Si) solar cell as the bottom cell, we investigate the relationship between the localized surface plasmon resonance effect of gold nanoparticles (AuNPs) and the arrangement of AuNPs onto solar cells. AuNPs were deposited on P-type crystalline Si (c-Si) cells and Si heterojunction (SHJ) type cells. To obtain the localized surface plasmon resonance effect, the shape, size, and arrangement of the nanostructures are important. Especially, arrangement of AuNPs onto solar cells was inquired in this study because these parameters must be adjusted appropriately to produce a plasmon resonance in a specific wavelength range. It was found that the plasmon resonance effect is significant when deposited on the surface of c-Si cell rather than on top of the Ag electrode. AuNPs deposition on the c-Si cell surface leads to not only the localized surface plasmon resonance effect but also improvement in charge transport between the c-Si cell surface and Ag electrode. However, in the SHJ-type cells, the plasmon resonance effect was not observed because the surface layer was composed of a W-doped In2O3 (IWO) layer. [ABSTRACT FROM AUTHOR]

Wide-bandgap (WBG) perovskite has demonstrated great potential in perovskite-based tandem solar cells. The power conversion efficiency (PCE) of such devices has surpassed 34%, signifying a new era for renewable energy development. However, the ion migration reduces the stability and hinders the commercialization, which is yet to be resolved despite many attempts. A big step forward has now been achieved by the simulation method. The detailed thermodynamics and kinetics of the migration process have been revealed for the first time. The stability has been enhanced by more than 100% via the heterojunction layer on top of the WBG perovskite film, which provided extra bonding for kinetic protection. Hopefully, these discoveries will open a new gate for WBG perovskite research and accelerate the application of perovskite-based tandem solar cells.

Tandem solar cells have the potential to surpass conventional single-junction photovoltaics by harnessing a wider range of the solar spectrum and reducing losses caused by thermalization and transmission. This study examines the performance of a kesterite-kesterite tandem solar cell with two different absorber layers in each subcell using SCAPS-1D. The upper subcell comprises CZTS and ACZTS with wider bandgaps, while the lower subcell comprises ACZTSe and CZTSe with narrower bandgaps. The CZTS- and CZTSe-based solar cells were first validated using experimental data to determine the feasibility of the tandem solar cell design. The CZTS-based solar cell was modified by replacing the back contact, adding a Cd-free buffer layer of ZnMnO, and using a SnMnO2 layer as a window layer. The band gap and electron affinity of ZnMnO and SnMnO2 layers were adjusted by changing their manganese contents for optimal conduction band offset. A thin ACZTS layer was also added as a second absorber layer in the CZTS-based solar cell to enhance open circuit voltage. The CZTSe-based solar cell was thereafter modified by including an ACZTSe layer as a second absorber layer and by selecting ZnSe as a buffer layer and optimizing the thicknesses of all layers. Both upper and lower subcells were analyzed for tandem configuration using filtered spectra and current-matching techniques. The thickness of the CZTS layer in the upper subcell was adjusted to achieve current matching; consequently, the proposed tandem cell had an efficiency of ∼24%. These findings provide valuable insights for future advancements in kesterite-kesterite-based tandem solar cells.

This paper presents research on the deposition of an indium tin oxide (ITO) layer which may act as a recombination layer in a silicon/perovskite tandem solar cell. ITO was deposited by magnetron sputtering on a highly porous surface of silicon etched by the metal-assisted etching method (MAE) for texturing as nano and microwires. The homogeneity of the ITO layer and the degree of coverage of the silicon wires were assessed using electron microscopy imaging techniques. The quality of the deposited layer was specified, and problems related to both the presence of a porous substrate and the deposition method were determined. The presence of a characteristic structure of the deposited ITO layer resembling a "match" in shape was demonstrated. Due to the specificity of the porous layer of silicon wires, the ITO layer should not exceed 80 nm. Additionally, to avoid differences in ITO thickness at the top and base of the silicon wire, the layer should be no thicker than 40 nm for the given deposition parameters. [ABSTRACT FROM AUTHOR]

In order to surmount the Shockley–Queisser efficiency barrier of single-junction solar devices, tandem solar cells (TSCs) have shown a potential solution. Organic and Si materials can be promising candidates for the front and rear cells in TSCs due to their non-toxicity, cost-effectiveness, and possible complementary bandgap properties. This study researches a flexible two-terminal (2-T) organic/Si TSC through TCAD simulation. In the proposed configuration, the organic solar cell (OSC), with a photoactive optical bandgap of 1.78 eV, serves as the front cell, while the rear cell comprises a Si cell based on a thin 70 μm wafer, with a bandgap energy of 1.12 eV. The individual standalone front and bottom cells, upon calibration, demonstrate power conversion efficiencies (PCEs) of 11.11% and 22.69%, respectively. When integrated into a 2-T organic/Si monolithic TSC, the resultant tandem cell achieves a PCE of 20.03%, indicating the need for optimization of the top organic cell to beat the efficiency of the bottom Si cell. To enhance the performance of the OSC, some design ideas are presented. Firstly, the OSC is designed by omitting the organic hole transport layer (HTL). Consequently, through engineering the front contact work function, the PCE is enhanced. Moreover, the influence of varying the absorber defect density of the top cell on TSC performance is investigated. Reduced defect density led to an overall efficiency improvement of the tandem cell to 23.27%. Additionally, the effects of the variation of the absorber thicknesses of the top and rear cells on TSC performance metrics are explored. With the matching condition design, the tandem efficiency is enhanced to 27.60%, with VOC = 1.81 V and JSC = 19.28 mA/cm2. The presented simulation results intimate that the OSC/Si tandem design can find applications in wearable electronics due to their flexibility, environmentally friendly design, and high efficiency.

The power conversion efficiency of all-inorganic Sb2S3-on-Si two-terminal (2-T) monolithically integrated and four-terminal (4-T) mechanically stacked tandem solar cells are investigated. A one-dimensional solar cell capacitance simulator (SCAPS-1D) has been used to simulate the stand-alone antimony trisulfide (Sb2S3) top sub-cell, silicon (Si) bottom sub-cell, 2-T monolithic, and 4-T mechanically stacked tandem solar cells. The stand-alone sub-cells are optimized by extensive studies, including interface defects density, bulk defects density, absorber layer thickness, and series resistance. The power conversion efficiency (PCE) of simulated stand-alone sub-cells is compared and verified with the existing literature. A current matching condition is established to characterize the 2-T monolithic Sb2S3-on-Si tandem cell. A filtered spectrum has been utilized for bottom sub-cell measurement in the tandem solar cells. The best-simulated PCE of Sb2S3-on-Si 2-T monolithic and 4-T tandem cells is 30.22% and 29.30%, respectively. The simulation results presented in this paper open an opportunity for the scientific community to consider Sb2S3 as a potential top sub-cell material in Sb2S3-on-Si tandem solar cells with high PCE. [ABSTRACT FROM AUTHOR]

Silicon-based tandem solar cells with efficient use of the solar spectrum are desirable for a next generation-commercial photovoltaic system. It has been widely investigated elsewhere using perovskites or III-V cells as top cell materials for high efficiency and stability. However, perovskite and III-V top cells are still unsuitable for mass production as well as expansion and integration with silicon solar cell production processes so far. Two-terminal bifacial Si/Si tandem cell by bonding with transparent conductive adhesive (TCA) is reported here. The current matching can maximize the efficiency by controlling the opening area of the top cell, which makes the bottom cell also able to absorb sunlight in the short wavelength region that is absorbed by the top cell as well, without being limited to the thickness or bandgap of the top cell. The Si/Si tandem solar cell achieved short circuit current density of 25.195 mA/cm2 after current matching by 36% opening ratio of top cell.

Optical and electrical features of halide perovskites make them commercially attractive high-efficiency solar cell absorbers. As a result, perovskite/silicon tandem solar cells have recently garnered the scientific community’s attention due to their better efficiency than single-junction solar cells. The most researched perovskite solar cell (PSC) is based on methylammonium lead iodide perovskite type; nevertheless, mixed cation/anion perovskites show better performances. Compositional engineering of perovskite allows us to screen for more efficient and stable materials. To better understand perovskite/silicon tandem performance, we systematically analyse the impact of compositions on device output under standard testing conditions and real-world climate using an opto-thermal model. Regional cell temperature and energy yield potential for variable perovskite compositions and bandgaps, FAxMA(1−x)Pb(BryI(1−y))3, are investigated. The optimal band gaps for bottom cells using Si (1.12 eV) and perovskite top cells (around 1.5–2.1 eV) are studied for realistic climate conditions. With a bandgap of 1.7 eV, the compound MAPbBrI 2 exhibited the best opto-electronic performance in tandem cells. Globally, Perovskite/silicon tandem cells (except 2.1 eV top cell perovskite) performed thermally better than Silicon solar cells due to the increased efficiency of tandem devices. The world-wide average perovskite cell temperature reduction was −3.9 °C, whereas the average energy generated was 26.7% higher relative to silicon solar cells. The current study will be extended by analysing the temperature coefficient’s sensitivity and employing realistic solar cell architectures.

The low bandgap antimony selenide (Sb2Se3) and wide bandgap organic solar cell (OSC) can be considered suitable bottom and top subcells for use in tandem solar cells. Some properties of these complementary candidates are their non-toxicity and cost-affordability. In this current simulation study, a two-terminal organic/Sb2Se3 thin-film tandem is proposed and designed through TCAD device simulations. To validate the device simulator platform, two solar cells were selected for tandem design, and their experimental data were chosen for calibrating the models and parameters utilized in the simulations. The initial OSC has an active blend layer, whose optical bandgap is 1.72 eV, while the initial Sb2Se3 cell has a bandgap energy of 1.23 eV. The structures of the initial standalone top and bottom cells are ITO/PEDOT:PSS/DR3TSBDT:PC71BM/PFN/Al, and FTO/CdS/Sb2Se3/Spiro-OMeTAD/Au, while the recorded efficiencies of these individual cells are about 9.45% and 7.89%, respectively. The selected OSC employs polymer-based carrier transport layers, specifically PEDOT:PSS, an inherently conductive polymer, as an HTL, and PFN, a semiconducting polymer, as an ETL. The simulation is performed on the connected initial cells for two cases. The first case is for inverted (p-i-n)/(p-i-n) cells and the second is for the conventional (n-i-p)/(n-i-p) configuration. Both tandems are investigated in terms of the most important layer materials and parameters. After designing the current matching condition, the tandem PCEs are boosted to 21.52% and 19.14% for the inverted and conventional tandem cells, respectively. All TCAD device simulations are made by employing the Atlas device simulator given an illumination of AM1.5G (100 mW/cm2). This present study can offer design principles and valuable suggestions for eco-friendly solar cells made entirely of thin films, which can achieve flexibility for prospective use in wearable electronics. [ABSTRACT FROM AUTHOR]

Shockley Queisser's theory states that the efficiency of single-junction solar cells is restricted. This constraint can be avoided by employing a tandem (stacking multiple cells) setup. Furthermore, stacking layers such as Perovskite/silicon in tandem architecture might boost efficiency. In this research, SCAPD-1D was used to simulate a monolithic 2T Perovskite/silicon tandem solar cell. The tandem configuration is composed of a narrow bandgap (1.1 eV) crystalline silicon Heterojunction with an intrinsic thin layer (HIT) solar cell at the bottom and a wide bandgap (1.8 eV) lead-free Perovskite (Cs2AgBi0.75Sb0.25Br6) solar cell on top. The proposed tandem device is simulated as a standalone and integrated structure. The PCE of the calibrated standalone cell is 14.54% (top cell) and 21.66% (bottom cell), respectively. The calibrated cells are used to design an integrated tandem configuration. The current matching condition is accomplished at varied thicknesses of top and bottom absorber layers. A bottom cell's ideal current matching thickness is 230 µm, while a perovskite top cell is 550 nm. The overall conversion efficiency of the tandem device is 26%, with an FF of 79.18%. [ABSTRACT FROM AUTHOR]

The current study introduces a two-terminal (2T) thin-film tandem solar cell (TSC) comprised of a polymer-based top sub cell and a thin crystalline silicon (c-Si) bottom sub cell. The photoactive layer of the top sub cell is a blend of PDTBTBz-2F as a polymer donor and PC71BM as a fullerene acceptor. Initially, a calibration of the two sub cells is carried out against experimental studies, providing a power conversion efficiency (PCE) of 9.88% for the top sub cell and 14.26% for the bottom sub cell. Upon incorporating both sub cells in a polymer/Si TSC, the resulting cell shows a PCE of 20.45% and a short circuit current density (Jsc) of 13.40 mA/cm2. Then, we optimize the tandem performance by controlling the valence band offset (VBO) of the polymer top cell. Furthermore, we investigate the impact of varying the top absorber defect density and the thicknesses of both absorber layers in an attempt to obtain the maximum obtainable PCE. After optimizing the tandem cell and at the designed current matching condition, the Jsc and PCE of the tandem cell are improved to 16.43 mA/cm2 and 28.41%, respectively. Based on this TCAD simulation study, a tandem configuration established from an all thin-film model may be feasible for wearable electronics applications. All simulations utilize the Silvaco Atlas package where the cells are subjected to standard one Sun (AM1.5G, 1000 W/m2) spectrum illumination. [ABSTRACT FROM AUTHOR]

Barium di-silicide (BaSi2) material has attracted noteworthy interest in photovoltaics, thanks to its stability, abundant nature, and excellent production feasibility. In this current work, a two-terminal (2T) monolithic all-BaSi2 tandem solar cell is proposed and explored through extensive TCAD simulation. A BaSi2 bottom sub-cell with a bandgap of 1.3 eV, and a Ba(CxSi1−x)2 top sub-cell with a tunable bandgap are employed in the design. It was found that a bandgap of 1.8 eV, which corresponds to x = 0.78, is the optimum choice to obtain the maximum initial power conversion efficiency (η) of 30%. Then, the tandem performance is optimized by investigating the impact of doping and the thickness of both absorber layers. Further, the current matching point is monitored whilst altering the thickness of the top cell resulting in η = 32.83%%, and a short-circuit current density (Jsc) of 16.47 mA/cm2. Additionally, we have explored the influence of the defect density in the absorbers, and the work function of contacts on the performance parameters. All TCAD simulations are accomplished using the Silvaco Atlas package under AM1.5G illumination. [ABSTRACT FROM AUTHOR]

Perovskite-based solar cells are a promising photovoltaic technology capable of offering higher conversion efficiency at low costs compared with the standard of the market. They can be produced via a thin film technology that allows for considerable environmental sustainability, thus representing an efficient, sustainable, flexible, and light solution. Tandem solar cells represent the next step in the evolution of photovoltaics (PV). They promise higher power conversion efficiency (PCE) than those currently dominating the market. The tandem solar cell design overcomes the limitations of single junction solar cells by reducing the thermal losses as well as the manufacturing costs. Perovskite has been employed as a partner in different kinds of tandem solar cells, such as the Si and CIGS (copper indium gallium selenide) based cells that, in their tandem configuration with perovskite, can convert light more efficiently than standalone sub-cells. This brief review presents the main engineering and scientific challenges in the field. The state-of-the-art three main perovskite tandem technologies, namely perovskite/silicon, perovskite/CIGS, and perovskite/perovskite tandem solar cells, will be discussed, providing a side-by-side comparison of theoretical and experimental efficiencies of multijunction solar cells. [ABSTRACT FROM AUTHOR]

Tandem solar cells (TSCs) have attracted prodigious attention for their high efficiency, which can surmount the Shockley–Queisser limit for single-junction solar cells. Flexible TSCs are lightweight and cost-effective, and are considered a promising approach for a wide range of applications. In this paper, a numerical model, based on TCAD simulation, is presented to assess the performance of a novel two-terminal (2T) all-polymer/CIGS TSC. To confirm the model, the obtained simulation results were compared with standalone fabricated all-polymer and CIGS single solar cells. Common properties of the polymer and CIGS complementary candidates are their non-toxicity and flexibility. The initial top all-polymer solar cell had a photoactive blend layer (PM7:PIDT), the optical bandgap of which was 1.76 eV, and the initial bottom cell had a photoactive CIGS layer, with a bandgap of 1.15 eV. The simulation was then carried out on the initially connected cells, revealing a power conversion efficiency (PCE) of 16.77%. Next, some optimization techniques were applied to enhance the tandem performance. Upon treating the band alignment, the PCE became 18.57%, while the optimization of polymer and CIGS thicknesses showed the best performance, reflected by a PCE of 22.73%. Moreover, it was found that the condition of current matching did not necessarily meet the maximum PCE condition, signifying the essential role of full optoelectronic simulations. All TCAD simulations were performed via an Atlas device simulator, where the light illumination was AM1.5G. The current study can offer design strategies and effective suggestions for flexible thin-film TSCs for potential applications in wearable electronics. [ABSTRACT FROM AUTHOR]

Tandem solar cells usually use a wide band gap absorber for top cell. The band gap of CuIn(1−x)GaxSe2 can be changed from 1.04 eV to 1.68 eV with the ratio of Ga/(In+Ga) from 0 to 1. When the ratio of Ga/(In+Ga) is over 0.7, the band gap of CIGS absorber is over 1.48 eV. CIGS absorber with a high Ga content is a possible candidate one for the top cell. In this work, CuInGa precursors were prepared by magnetron sputtering with CuIn and CuGa targets, and CIGS absorbers were prepared by selenization annealing. The Ga/(In+Ga) is changed by changing the thickness of CuIn and CuGa layers. Additionally, CIGS solar cells were prepared using CdS buffer layer. The effects of Ga content on CIGS thin film and CIGS solar cell were studied. The band gap was measured by PL and EQE. The results show that using structure of CuIn/CuGa precursors can make the band gap of CIGS present a gradient band gap, which can obtain a high open circuit voltage and high short circuit current of the device. With the decrease in Ga content, the efficiency of the solar cell increases gradually. Additionally, the highest efficiency of the CIGS solar cells is 11.58% when the ratio of Ga/(In+Ga) is 0.72. The value of Voc is 702 mV. CIGS with high Ga content shows a great potential for the top cell of the tandem solar cell. [ABSTRACT FROM AUTHOR]

The design of multi-junction solar cells is guided by both the theoretical optimum bandgap combinations as well as the realistic limitations to materials with these bandgaps. Nowadays, triple-junction III-V multi-junction solar cells are commonly used as GaAs, InGaAs; InGaP ... In this work, we are interested in studying triple junctions based on thin-film solar cells Cu(In1-xGax) Se2, CuInSe2, and CuGaSe2 quaternaries using Silvaco ATLAS software. Incorporating Cu(In0.34Ga0.66) Se2 as an absorber in the middle sub-cell increased the open-circuit voltage by 0.72 V. The highest cell efficiency is 20.89 % (Voc = 2.33 V, Jsc = 9.97 mA/cm2, FF = 89.62%). This triple-junction solar cell demonstrates the potential and limitations of future improvements when voltage and current are considered.

• The interference effect is a vital factor that needs to be considered when improving solar cell's performance and making accurate measurements. • Different influences of interference effects introduced by transparent conductive oxide and metal electrodes were investigated. • The thickness of indium zinc oxide (IZO) film should be set to 200 nm to match the current in perovskite/silicon monolithic tandem solar cells when considering the interference effect. • IZO thickness, absorber thickness and bandgap need to be modified synergistically for a tandem solar cell if the interference effect is introduced. In recent years, there has been rapid developments of both single-junction and tandem solar cells based on metal halide perovskite, which both require metal electrodes or transparent conductive electrodes. In the present study, interference effects induced by electrodes are investigated to reveal the light field distribution in perovskite absorbers. The results show that the interference effect occurring near the absorption edge will lead to complicated light distribution, which supposedly influences the location of carrier generation. The interference effect introduced by transparent electrodes can influence the current matching between sub-cells of perovskite/silicon monolithic tandem solar cells. As revealed through calculations, an indium zinc oxide (IZO) electrode with a thickness of 200 nm is beneficial for current matching. The optimal power conversion efficiency (PCE) is achieved when the thickness is increased to 250 nm, which could be attributed to lower sheet resistance of the IZO electrode improving the fill factor of the current density–voltage (J-V) curve. However, further increasing the thickness results in reduced PCE due to the decreased average transmittance of the IZO electrode. This work provides a strategy for selecting the proper thickness of a transparent electrode and perovskite absorber for a solar cell, and thus, can facilitate design and fabrication of devices for practical application. [ABSTRACT FROM AUTHOR]

Optical design, photon management, and energy conversion efficiency are investigated through numerical simulation of perovskite/silicon tandem solar cell using the single-diode model. A strong near-infrared reflectance of roughly 60% is present in the perovskite-based top cell. ZnO and Si3N4 anti-reflection coating layers are placed on the surface of the perovskite layer and silicon sub-cell of the tandem solar cell respectively for photon management and minimizing the near-infrared reflectance loss. ZnO will act as an electron transport layer as well as an anti-reflection coating layer. The ZnO layer will minimize the near-infrared reflectance loss by the top cell in the device structure and allow the maximum transmittance of near-infrared photon energy to the silicon sub-cell. Intermediate anti-reflection Si3N4 layer assists in the maximum localization of the transmitted near-infrared photon energy in the silicon sub-cell. The efficiency of over 32% is achieved by optimizing the parameters of different materials such as perovskite, silicon, and anti-reflection coating layer in the tandem solar cell. The innovative idea of using electron transport material ZnO as an anti-reflection coating layer in the perovskite-based top cell can minimize the reflection loss by nearly 20%. The combination of ZnO and Si3N4 anti-reflection coating layers improved the conversion efficiency of the tandem cell by 1%. This result paves the way to realize highly efficient tandem solar cells through photon management. [ABSTRACT FROM AUTHOR]

We report the development of AlInP‐passivated solar cells grown by dynamic hydride vapor‐phase epitaxy (D‐HVPE) with AM1.5G efficiencies of 26.0% for single‐junction (1J) GaAs cells and 28.0% for GaInP/GaAs (2J) tandems. We compare the device performance of solar cells passivated with AlInP versus control cells passivated with GaInP, which has already enabled near‐unity carrier collection in GaAs solar cells. 1J devices passivated with either AlInP or GaInP have an identical open‐circuit voltage (VOC) of 1.06 V and long‐wavelength current collection near 95%, indicating that both window materials provide a similar degree of passivation. Adding AlInP passivation to each solar cell structure improves the current collection by 1.3 and 1 mA/cm2 for the 1J and 2J, respectively. The AlInP also results in a top cell VOC boost of ~40 mV relative to a tandem device passivated only by a thin, highly doped GaInP emitter. Secondary‐ion mass spectrometry measurements indicate that although O and Si both incorporate in the AlInP window, they do not appear in the subsequently grown absorber layers and do not impact its ability to passivate the front surface. We expect that these achievements, along with continued optimization, will enable parity of hydride vapor‐phase epitaxy (HVPE)‐grown device efficiencies with state‐of‐the‐art devices grown by other epitaxial methods in the near future. [ABSTRACT FROM AUTHOR]

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Light‐trapping elements play an important role in solar cells to enhance their light‐harvesting efficiency. Pyramidal‐shaped nano‐microstructures and gradient metasurfaces are mostly used as light‐trapping elements in solar cells. There is, however, one major concern with nanostructured solar cells: a larger surface area resulting in a larger surface recombination loss. In this article, a novel thin‐film wedge tandem‐solar cell made of perovskites and silicon is designed where the bottom cell itself works as a light‐trapping element. Optical and electrical simulations are performed to estimate performance metrics of the wedge tandem‐solar cell and compare with typically used unpatterned planar tandem‐solar cell. In terms of optical and electrical performance, wedge geometry outperforms planar geometry and shows 17.18% higher efficiency. Compared to a typical planar tandem cell, such a design can lead to thin and low‐weight tandem solar cells, which can be very useful in space applications. The proposed design can be fabricated using an optimized electrospray deposition process. [ABSTRACT FROM AUTHOR]

Monolithic hybrid halide perovskite/crystalline silicon (c-Si) tandem solar cells have demonstrated their great potential to surpass the theoretical efficiency limit of single-junction devices. However, the stability of perovskite sub-cells is inferior to that of the c-Si solar cells that have been commercialized, casting serious doubt about the lifetime of the entire device. During device operation, light and heat are inevitable, which requires special attention. Herein, we review the current understandings of the intrinsic stability of perovskite/c-Si tandems upon light and/or heat aging. First, we summarize the recent understandings regarding light facilitated ion migration, materials decomposition, and phase segregation. In addition, the reverse bias effect on the stability of tandem modules caused by uneven illumination is discussed. Second, this review also summarizes the thermal-induced degradation and mismatch issue, which underlines the system design of perovskite/c-Si tandems. Third, recent strategies to improve the intrinsic stability of perovskite/c-Si tandems under light and/or heat are reviewed, such as composition engineering, crystallinity enhancement, interface modification, material optimization, and device structure modification. At last, we present several potential research directions that have been overlooked, and hope those are helpful for future research on perovskite based tandem solar cells. [ABSTRACT FROM AUTHOR]

Inorganic-organic metal halide perovskite light harvester-based perovskite solar cells (PSCs) with widely tunable bandgap have achieved rapid growth in power conversion efficiency, which exceeds 25% now. It is deliberated that if a semitransparent solar cell made of wider bandgap materials was placed on top of a narrow bandgap materials-based solar cell such as a silicon solar cell, with proper optical and electrical arrangements, the resultant tandem device consisting of two subcells could more effectively utilize the solar spectrum than a single junction solar cell. In a perovskite/silicon tandem solar cell (PSTSC), a semitransparent PSC with a wider bandgap is placed on top of a narrow bandgap silicon solar cell. The PSC efficiently harvests the higher energy photons in the ultraviolet and visible regions of the solar spectrum while the silicon solar cell can convert the photons of the infrared region to power. The PSTSC is proposed as a potential candidate to overcome the Shockley-Queisser limit of single-junction silicon solar cells. Though the theoretical limit of a PSTSC is calculated as ∼42%, its actual efficiency achieved until now is less than 30%. Therefore, a great scope of research exists in improving the efficiency of PSTSCs. Current issues of stability and upscaling of the device in PSCs are also a matter of concern for PSTSCs. A tandem device consists of multiple parts, and different configurations can be applied, thus tuning the architecture of the device. Altering various parts may result in significant changes in the efficiency of the device. In this review, competing architectures of otherwise comparable devices are compared in terms of photovoltaic properties. Thus, future directions to improve the efficiency of the device based on architecture design are proposed herein. In particular, the influence of the polarity of PSCs and the surface morphology of silicon solar cells (both front and rear) on determining the properties of the PSTSC are discussed. [ABSTRACT FROM AUTHOR]

Perovskite-silicon tandem solar cells have shown great potential in increasing the efficiency of solar cells, with efficiencies reaching as high as 25%. However, the stability of these cells remains a major challenge that must be addressed before they can be commercialized. This review focuses on the stability challenges of perovskite-silicon tandem solar cells and possible solutions to address these challenges. Author's performed systematic review of the literature for Stability Challenges and Probable Solution of Perovskite-Silicon Tandem Solar Cells. The main stability issues include the instability of the perovskite layer, the degradation of the silicon layer, and the failure of the interfaces between the layers. One solution is to use more stable perovskite materials, such as methylammonium lead iodide (MAPbI3) or formamidinium lead iodide (MAPbI3), which have shown better stability than traditional perovskite materials. Another solution is to use passivating layers, such as titanium dioxide, to protect the perovskite layer from degradation. Another solution is to use silicon heterojunction (SHJ) solar cells, which have shown better stability than traditional silicon solar cells. In addition, the use of encapsulation techniques, such as using a barrier layer or a hermetic seal, can help to protect the tandem solar cell from environmental degradation. In order to improve the stability of perovskite-silicon tandem solar cells, it is important to continue research on the development of more stable perovskite materials, passivating layers, and encapsulation techniques. Perovskite-silicon tandem solar cells are of significant interest due to several reasons. It has high efficiency, Complementary absorption properties, Cost-effectiveness, Versatility and scalability, Potential for high power output. Despite their immense promise, perovskite-silicon tandem solar cells still face challenges such as long-term stability, material compatibility, and largescale manufacturing which need to be addressed in the near future. Additionally further research is needed to understand the mechanisms of degradation and to develop methods for monitoring and mitigating the degradation of the tandem solar cells. [ABSTRACT FROM AUTHOR]

Potentially temperature-resistant inorganic perovskite/silicon tandem solar cells (TSCs) are promising devices for boosting efficiency past the single-junction silicon limit. However, undesirable non-radiative recombination generally leads to a significant voltage deficit. Here, we introduce an effective strategy using nickel iodide, an inorganic halide salt, to passivate iodine vacancies and suppress non-radiative recombination. NiI2-treated CsPbI3-xBrx inorganic perovskite solar cells with a 1.80 ​eV bandgap exhibited an efficiency of 19.53% and a voltage of 1.36 ​V, corresponding to a voltage deficit of 0.44 ​V. Importantly, the treated device demonstrated excellent operational stability, maintaining 95.7% of its initial efficiency after maximum power point tracking for 300 ​h under continuous illumination in a N2 atmosphere. By combining this inorganic perovskite top cell with a narrower bandgap silicon bottom cell, we for the first time achieved monolithic inorganic perovskite/silicon TSCs, which exhibited an efficiency of 22.95% with an open-circuit voltage of 2.04 ​V. This work provides a promising strategy for using inorganic passivation materials to achieve efficient and stable solar cells.

• An in-depth DFT study was conducted on C s 2 S c A g X 6 (X = Br, I) double halide perovskites, analyzing structural, optical, and electronic properties.. • Band structures and density of states indicate key photovoltaic applications. • The gap energy of C s 2 S c A g I 6 favors its use as an absorber in tandem solar cells. • SCAPS-1D simulation of a Cs 2 ScAgI 6 /CIGS tandem cell achieved 28.88% efficiency. Double perovskites, which have substantial benefits over conventional lead-based perovskites in terms of chemical stability and non-toxicity, have become a viable substitute in recent years. This study provides a comprehensive evaluation of C s 2 S c A g X 6 (X = Br, I) as a potential photovoltaic (PV) material, based on a density functional (DFT) calculation using the generalised gradient approach (GGA) with the modified Becke-Johnson (mBJ) potential, which show that this material is characterised by a band gap of 1.8 eV for X = Br and 1.55 eV for X = I, as well as excellent optical properties, including a high absorption coefficient greater than 10 5 c m - 1 . The results obtained highlight the suitability of C s 2 S c A g X 6 as a photovoltaic material. More specifically, it can play the role of absorber for the top cell in tandem solar cells. This study focuses on the use of C s 2 S c A g I 6 as an absorber for top cell, in combination with CIGS as an absorber for bottom cell, to construct a two-junction tandem solar cell. Current matching, essential for the operation of the tandem cell, is achieved by using a filtered spectrum to illuminate the lower cell, pre-calibrated based on experimental values from the literature. This condition is achieved with a thickness of 490 nm of C s 2 S c A g I 6 , offering exceptional performance: 1.795 V for the open circuit voltage (V o c), 18.45 mA/ c m 2 for the short-circuit current density (J s c), a fill factor (FF) of 87.2 %, and a power conversion efficiency (PCE) of 28.88 %. [ABSTRACT FROM AUTHOR]

• Lead (Pb)-free perovskite Cs 2 SnI 6-n Br n can used as a top cell absorber for silicon heterojunction (SHJ) tandem solar cells. • Cs 2 SnI 5 Br/SHJ tandem solar cell with 39.1% PCE is achieved theoretically. • Highly stable and environment-friendly Cs 2 SnI 6-n Br n has the potential to replace toxic and unstable perovskites. Emerging Lead (Pb)-free perovskite solar cells are environment-friendly and show higher stability. Such materials are considered the future of the photovoltaic industry. However, the detailed understanding of these materials is still very limited experimentally as well as theoretically. In this work, all inorganic Pb-free perovskites Cs 2 SnI 6-n Br n have been studied as top cell materials for silicon heterojunction (SHJ)-based tandem solar cells. The optoelectronics characteristics including bandgap, optical absorption, effective masses and carrier mobility of Cs 2 SnI 6-n Br n have been calculated by the first-principle with varying Br- alloying. Details theoretical study show that the bandgap of Cs 2 SnI 6-n Br n can tuned over a range of 1.05 eV to 1.99 eV. In addition, carrier mobility has been modelled for the studied perovskites by deformation potential theory. Based on the calculated optoelectronics characteristics, a standalone Cs 2 SnI 6-n Br n solar cell is simulated and 20.5 % efficiency is reported. SHJ-based solar cell is used as the bottom cell with 28.5 % standalone efficiency under standard spectrum illuminations. Finally, the Cs 2 SnI 6-n Br n /SHJ tandem solar cell is designed and a simulated PCE of 39.1 % has been achieved with n = 1. The highest 1.46 V Voc is obtained with a 40.5 mA/cm2 matched current between the top and bottom cells. The proposed work gives a detailed study of Cs 2 SnI 6-n Br n perovskites and is expected to facilitate the production of Pb-free perovskites/SHJ tandem solar cells. [ABSTRACT FROM AUTHOR]