Tandem Cells Research Articles

Bimolecular Crystallization Modulation Boosts the Efficiency and Stability of Methylammonium‐Free Tin–Lead Perovskite and All‐Perovskite Tandem Solar Cells

AbstractThe elimination of methylammonium (MA) cation from mixed tin–lead (Sn–Pb) narrow‐bandgap (NBG) perovskites is an effective approach to enhance the operational stability of all‐perovskite tandem solar cells (TSCs). Unfortunately, the uncontrolled nucleation and crystallization processes of MA‐free Sn–Pb perovskites usually lead to inferior film quality and device performance. Herein, a bimolecular crystallization modulation strategy is reported by using guanidine thiocyanate (GuaSCN) and aminoacetamide hydrochloride (AHC) together as additives to improve the film quality of MA‐free Sn–Pb perovskites. It is demonstrated that the use of bimolecular additives can effectively improve the crystallinity, increase the grain size, and induce a preferred (100) orientation for the corresponding films, leading to high‐quality absorber with considerably reduced defect density and suppressed non‐radiative recombination. In addition, the bimolecular additives can reduce the self‐p‐doping hole concentration within the perovskite films and enhance the charge extraction at the perovskite/electron transport layer interface. The modified NBG perovskite solar cells deliver a power conversion efficiency (PCE) of 22.14%. Coupled with the wide‐bandgap (WBG) subcell, the all‐perovskite TSCs give a champion certified PCE of 27.15%, which is the highest certified PCE for MA‐free all‐perovskite TSCs. Encapsulated tandem devices maintain 90% of the initial PCE after 473 h operation.

Effects of Photon Recycling and Luminescent Coupling in All‐Perovskite Tandem Solar Cells Assessed by Full Opto‐electronic Simulation

The impact of photon recycling (PR) and of luminescent coupling (LC) on the photovoltaic performance of all‐perovskite tandem solar cells is analyzed by the means of optical and full opto‐electronic device simulation. Optical processes are assessed using a comprehensive Green function formalism that considers wave optical effects also in emission. Starting from a consistent fit of experimental sub‐cell and tandem characteristics, the effects of re‐absorption are propagated from the optical limit to a situation with consideration of realistic charge transport across the entire tandem device. This also provides insight into the origin of performance losses due to sub‐cell and interconnection quality.

Full optoelectronic simulation of all antimony chalcogenide thin film tandem solar cell: Design routes from 4-T to 2-T configuration

Antimony chalcogenide, as a newcomer to light harvesting materials, is regarded as an auspicious contender for incorporation as a photoactive layer in thin film tandem solar cells (TFTSCs). The current study introduces the design of all-antimony chalcogenide TFTSC comprised of an Sb2S3 (1.7 eV) front subcell and an Sb2Se3 (1.2 eV) rear subcell. The challenges to migrating from four-terminal (4-T) to two-terminal (2-T) designs are highlighted and possible solutions are proposed. To commence, a calibration procedure for the two subcells is conducted in alignment with experimental investigations. The benchmarked solar cells yield a power conversion efficiency (PCE) of 8.08 % for the upper subcell and 10.58 % for the lower subcell. Subsequently, upon integration of both subcells within the initial 4-T Sb2S3/Sb2Se3 TFTSC, the resultant PV cell attains a PCE of 12.27 %. Before transitioning it to a more efficient 2T tandem configuration, we explore alternative inorganic HTL materials to the Spiro-OMeTAD HTL to overcome its practical considerations. Cu2O is found to be the best HTL alternative to be included for both subcells. Upon stacking into the tandem structure, the combined cell exhibited an efficiency of 15.68 % and a notable Jsc of 16.23 mA/cm2. To further enhance the tandem performance, the device structure is optimized by engineering the CBO of two sub-cells and employing a double ETL design for the front sub-cell. At the considered current matching criterion, the tandem device PCE and Jsc are boosted to 27.86 % and 17.60 mA/cm2, respectively. Based on this full optoelectronic analysis, developed in the Silvaco TCAD environment, a 2-T all antimony chalcogenide tandem configuration can be realized and optimized, paving the way for future experimental endeavors.

Defects analysis of radiation damage mechanism for IMM triple-junction solar cell under 1 MeV electron irradiation

Inverted metamorphic (IMM) GaInP/GaAs/InGaAs rigid triple-junction solar cells under 1 MeV electron irradiation at various fluences were investigated theoretically. By fitting the electrical and optical parameters of solar cells with experimental results at the fluence ranging from 1 × 1014 e cm−2 to 1 × 1015 e cm−2, basic trap information was obtained, and then the minority carrier lifetime and trap concentration of sub-cells at various fluences were also calculated. The defects analysis of IMM triple-junction solar cell presented in this work could help understanding the radiation damage mechanism of 1 MeV electron irradiation.

Non-destructive buffer enabling near-infrared-transparent inverted inorganic perovskite solar cells toward 1400 h light-soaking stable perovskite/Cu(In,Ga)Se2 tandem solar cells

Near-infrared (NIR) transparent inverted all-inorganic perovskite solar cells (PSCs) are excellent top cell candidates in tandem applications. An essential challenge is the replacement of metal contacts with transparent conductive oxide (TCO) electrodes, which requires the introduction of a buffer layer to prevent sputtering damage. In this study, we show that the conventional buffers (i.e., small organic molecules and atomic layer deposited metal oxides) used for organic-inorganic hybrid perovskites are not applicable to all-inorganic perovskites, due to non-uniform coverage of the vulnerable layers underneath, deterioration upon ion bombardment and moisture induced perovskite phase transition. A thin film of metal oxide nanoparticles by the spin-coating method serves as a non-destructive buffer layer for inorganic PSCs. All-inorganic inverted near-infrared-transparent PSCs deliver a PCE of 17.46% and an average transmittance of 73.7% between 780 and 1200 nm. In combination with an 18.56% Cu(In,Ga)Se2 bottom cell, we further demonstrate the first all-inorganic perovskite/CIGS 4-T tandem solar cell with a PCE of 24.75%, which exhibits excellent illumination stability by maintaining 86.7% of its initial efficiency after 1400 h. The non-destructive buffer lays the foundation for efficient and stable NIR-transparent inverted inorganic perovskite solar cells and perovskite-based tandems.

Water splitting system with a 13.1% solar to hydrogen conversion efficiency using 3-junction III-V solar cells with pulse plated Pt black catalyst

Abstract We report on a highly efficient system for water splitting using concentrator III-V triple-junction solar cells supported with a platinum black catalyst, which was plated on the surface electrodes of the solar cells under various conditions to improve the hydrogen conversion efficiency. We also reduced the path length of light in water to improve the power generation efficiency, reducing the absorption of near-infrared lights by water. As a result, we improved the solar-hydrogen conversion efficiency to 13.1% when irradiated with 1sun of pseudo-sunlight without external bias. This achievement is due to the large area ratio of Pt catalyst coverage.

Silicon / Perovskite Tandem Solar Cells with Reverse Bias Stability down to -40V. Unveiling the Role of Electrical and Optical Design.

The reverse bias stability is a key concern for the commercialization and reliability of halide perovskite photovoltaics. Here, the robustness of perovskite-silicon tandem solar cells to reverse bias electrical degradation down to -40V is investigated. The two-terminal tandem configuration, with the perovskite coupled to silicon, can improve the solar cell resistance to severe negative voltages when the tandem device is properly designed. While perovskite cells typically exhibit early reverse bias breakdown voltages, the serial connection with silicon cells with large shunt resistances and high voltage breakdown limits their negative polarization and prevent the passage of large current densities when reverse biased. The importance of careful optical design is illustrated, with bottom-limited conditions required to prevent the perovskite topcell from exploring its own breakdown. This aspect is of great importance in the case of partial shading events when the solar spectrum is richer in the IR components than the standard AM1.5G. Notably, 100% of efficiency retained after polarization at -40V in different stressing conditions is observed. The results presented suggest that standard industrial bypass diode schemes may be compatible with silicon/perovskite tandem photovoltaics and provide new guidelines for the standardization of the stressing protocols.

Role of NiO in wide-bandgap perovskite solar cells based on self-assembled monolayers

NiO/self-assembled monolayer (SAM) double hole transport layers (HTLs) has become the mainstream choice in high-efficiency single-junction and tandem perovskite solar cells (PSCs). However, the underlying role of NiO in double HTLs from the microscale is not systematically revealed currently. Herein, we reveal that NiO plays an important role in inducing a more uniform and thinner SAM from three aspects. Firstly, compared with indium tin oxide (ITO), the NiO surface exposes less crystal facet orientations and a higher metal atom density, suggesting that sufficient chemical binding sites for SAMs are provided to facilitate the close-packed assembly of SAMs. Secondly, NiO modified ITO exhibits smaller surficial roughness and strongly bonded −OH, which is beneficial to the uniform distribution of SAMs and strong adhesion to the NiO surface. Utilizing the well-constructed SAM, we fabricate wide-bandgap (>1.75 eV) PSCs using vacuum-assisted technology and achieve an impressive photoelectric conversion efficiency of 19.55 %. These findings not only deepen the understanding of SAM assembly on substrates but also provide essential guidance for the future industrialization of PSCs.

Midgap states and energy alignment at interconnect are crucial for perovskite tandem solar cells

Midgap states and energy alignment at interconnect are crucial for perovskite tandem solar cells

Interfacial engineering for efficient and stable two-terminal perovskite-based tandem solar cells

Interfacial engineering for efficient and stable two-terminal perovskite-based tandem solar cells

Improving the Open-Circuit Voltage of III–V Layer-Filtered Si Subcells for Monolithic III–V/Si Tandem Solar Cells

Improving the Open-Circuit Voltage of III–V Layer-Filtered Si Subcells for Monolithic III–V/Si Tandem Solar Cells

Development of Low-Cost c-Si-Based CPV Cells for a Solar Co-Generation Absorber in a Parabolic Trough Collector

Concentrator photovoltaics (CPVs) have demonstrated high electrical efficiencies and technological potential, especially when deployed in CPV–thermal (CPV-T) hybrid absorbers, in which the cells’ waste heat can be used to power industrial processes. However, the high cost of tracking systems and the predominant use of expensive multi-junction PV cells have caused the market of solar co-generation technologies to stall. This paper describes the development and testing of a low-cost alternative CPV cell based on crystalline silicone (c-Si) for use in a novel injection-molded parabolic hybrid solar collector, generating both, photovoltaic electricity and thermal power. The study covers two different c-Si cell technologies, namely, passive emitter rear contact (PERC) and aluminum back surface field (Al-BSF). Simulation design and manufacturing are described with special attention to fingerprinting in order to achieve high current carrying capacities for concentrated sunlight. It was determined that Al-BSF cells offer higher efficiencies than PERC for the considered use case. Solar simulator tests showed that the highly doped 4 cm2 cells (50 ohm/sq) reach efficiencies of 16.9% under 1 sun and 13.1% under 60 suns at 25 °C with a temperature coefficient of −0.069%(Abs)/K. Finally, options to further improve the cells are discussed and an outlook is given for deployment in a field-testing prototype.

Pyramid‐Shaped Perovskite Single‐Crystal Growth and Application for High‐Performance Photodetector

AbstractTo boost the power conversion efficiency of silicon/perovskite tandem solar cells, pyramid‐textured structures have been investigated and introduced into devices. However, high‐quality pyramid‐shaped single crystal preparation is an obstacle in tandem device development. Perovskite crystals obtained using general methods are cubic because of their structural symmetry and rapid growth rate. In this study, based on mass transfer boundary layer theory, a pyramid‐shaped perovskite single crystal is successfully obtained using an asymmetrically spatial confinement‐induced crystallization method. The synthesized pyramid crystals exhibited high crystallinity and enhanced optical absorption. A photodetector constructed using the as‐grown crystal exhibited high‐performance properties, including a responsivity of 9.4 A W−1, photo‐to‐dark current ratio of 2.3 × 104, and detectivity of 2.1 × 1011 Jones. Its unique insensitivity to the incident photon direction is also characterized. The flexible photodetector also exhibited excellent responsivity under different bending curvature radii. Additionally, the light‐trapping effect and absorption superiority of pyramid crystals over cuboid crystals are well established based on a semi‐empirical analytical model. This breakthrough in pyramid‐shaped perovskite crystal preparation provides a promising approach for the development of novel tandem solar cells and other optoelectronic devices.

Yielding high photovoltaic conversion efficiency by Pd-decoration on Si-based interface: A density-functional theory study

There has been showing great interest in boosting the performance of III-V/Si multi-junction solar cell, which is low-cost and offering high photovoltaic conversion efficiency. Adding noble-metal nano-array at the interface between the Si and III-V materials is one of most effective ways. This theoretical work comprehensively studied the atomic structure, electronic properties, and optical response of Pd-decoration on the Si(111) surface by using density-functional theory calculations. The structural stability calculations showed that Pd atoms could exist on Si surface in many forms. The calculated differential charge density with Bader charge showed that the charge transfer between Pd and Si atoms would increase the generation of electron-hole pairs. At the same time, Pd-decoration could reduce the work function and improve the optical conductivity of Si surface. In addition, the modification of Pd atoms would create new energy levels near the Fermi level in the band gap of Si surface. These energy levels enable Si bottom cell to undergo electron inter-band transitions under weak light irradiation, improving the utilization of weak light. This work provided a micro physical explanation for the improvement of III-V/Si solar cell by using noble-metal nano-array.

Solvent engineering for scalable fabrication of perovskite/silicon tandem solar cells in air

Perovskite/silicon tandem solar cells hold great promise for realizing high power conversion efficiency at low cost. However, achieving scalable fabrication of wide-bandgap perovskite (~1.68 eV) in air, without the protective environment of an inert atmosphere, remains challenging due to moisture-induced degradation of perovskite films. Herein, this study reveals that the extent of moisture interference is significantly influenced by the properties of solvent. We further demonstrate that n-Butanol (nBA), with its low polarity and moderate volatilization rate, not only mitigates the detrimental effects of moisture in air during scalable fabrication but also enhances the uniformity of perovskite films. This approach enables us to achieve an impressive efficiency of 29.4% (certified 28.7%) for double-sided textured perovskite/silicon tandem cells featuring large-size pyramids (2–3 μm) and 26.3% over an aperture area of 16 cm2. This advance provides a route for large-scale production of perovskite/silicon tandem solar cells, marking a significant stride toward their commercial viability.

Low-temperature growth of narrow optical gap highly conducting nc-Ge thin films with superior crystallinity involving dominant orientation

The nc-Ge thin films are grown at a moderately low temperature (∼220 °C) in rf PECVD via optimizing the GeH4 plasma with H2-dilution, within 97.5 ≤ D(H2)(%) ≤ 99.5. At elevated D(H2), while the bonded H-content in the matrix reduces, the film's crystallinity and dc conductivity increase. However, the optical band gap widens for 97.5 ≤ D(H2)(%) ≤ 98.5, via the elevated quantum confinement effect from the increased number of Ge-ncs of dimension below Bohr radius. Conversely, for D(H2) ≥ 98.5%, switching in the quantum effect in larger-sized Ge-ncs induces the band gap narrowing. Significantly reduced ultra-nanocrystalline-Ge (unc-Ge) component occupying the grain boundary zone, minimizes the contribution of grain-boundary defects. However, the persistent amorphous Ge matrix becomes highly defective and less dense, and those induce enhanced O-absorption from the ambient in the dominant Ge-Ox (x < 2) configuration. On increased crystallinity, the activation energies of dipole relaxation (ΔEτ) and resistance (ΔE) in the impedance data reduce dominantly in the a-Ge component than its nc-Ge counterpart, which occurs identically for the dc conductivity when the amorphous component in the matrix sharply disappears at increased D(H2) > 98.5%. A narrow band gap (∼0.90 eV), conducting (σd ∼3.0 ×10−2 S cm−1), and photosensitive nc-Ge network, involving dominant <111>-oriented Ge-ncs (∼35.2 nm) of enriched volume fraction (XC ∼90.2%), obtained at D(H2) ∼99.5%, seems extremely useful for need-based applications as a narrow band gap absorber layer in the bottom sub-cell of flexible high-efficiency cost-effective multijunction thin film solar cells.

Comprehensive design and analysis of thin film Sb2S3/CIGS tandem solar cell: TCAD simulation approach

This research presents a design and analysis of a tandem solar cell, combining thin film wide bandgap Sb2S3 (1.72 eV) and narrow bandgap CIGS (1.15 eV) for the top and bottom sub-cells, respectively. The integration of all thin film layers enhances flexibility, rendering the tandem solar cell suitable for applications such as wearable electronics. To optimize the power conversion efficiency (PCE) of the tandem solar device, advanced technology computer-aided design (TCAD) simulation tools are employed to estimate loss mechanisms and fine-tune parameters for each layer. An experimentally validated optoelectronic model is introduced, calibrated and validated against fabricated reference solar cells for the individual top and bottom cells. The calibrated model is then utilized to propose optimization routines for the Sb2S3/CIGS tandem solar cell. The initial tandem cell exhibits a J SC of 15.72 mA cm−2 and a PCE of 15.36%. The efficiency drop in the tandem configuration is identified primarily in the top cell. A systematic optimization process for the top cell is initiated, exploring various configurations, including HTL-free and ETL-free setups. Moreover, an np homojunction structure for the top cell is proposed. Optimization routines are applied that involve determining optimal thickness and doping concentration of the n-layer, investigating the effect of p-layer doping concentration, and exploring the influence of the work function of the front contact. As a result, the tandem cell efficiency is significantly improved to 23.33% at the current matching point (CMP), with a J SC of 17.15 mA cm−2. The findings contribute to the advancement of thin-film tandem solar cell technology, showcasing its potential for efficient and flexible photovoltaic applications.

Impact of Temperature Optimization of ITO Thin Film on Tandem Solar Cell Efficiency.

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.

High‐Performance Perovskite‐Based Tandem Solar Cells: Recent Advancement, Challenges, and Steps toward Industrialization

As a result of an ongoing global dedication, metal‐halide perovskite (PVSK) has proven to be a promising substitute among other developed materials for next‐generation photovoltaic cells due to significantly high efficiency, economical reasons, environmentally friendly processing, and bandgap alterations. In just 12 years, PVSK‐based single cells have achieved an efficiency of 26.1%, reaching single‐crystal silicon solar cells at 27.6% and silicon heterostructure solar cells at 26.8%. PVSK‐based tandem cells also have achieved remarkable attention as a viable candidate for future‐generation photovoltaic technology. Currently, a considerable number of reports are documented as evidence of the efforts to integrate the wide‐bandgap PVSK either with itself (narrow‐bandgap PVSK ([NBG‐PVSK]) or other traditional (NBG) cells, including silicon (Si), copper–indium–gallium–selenide, organic solar cells, cadmium telluride (CdTe), and dye‐sensitized. Thanks to the substantial growth made in the advances of PVSK‐based tandem cells both in the laboratories and in the commercialization sector, this review will systematically elucidate the emergence of PVSK‐based cells, their current status, and applications in tandem configurations. Furthermore, this survey will cover the analysis of different strategies and efforts to achieve cutting‐edge photovoltaic technology. Finally, the commercialization of different PVSK‐based tandem technologies and their prospects are analyzed.

Advances in Mixed Tin-Lead Narrow-Bandgap Perovskites for Single-Junction and All-Perovskite Tandem Solar Cells.

Organic-inorganic metal-halide perovskites have received great attention for photovoltaic (PV) applications owing to their superior optoelectronic properties and the unprecedented performance development. For single-junction PV devices, although lead (Pb)-based perovskite solar cells have achieved 26.1% efficiency, the mixed tin-lead (Sn-Pb) perovskites offer more ideal bandgap tuning capability to enable an even higher performance. The Sn-Pb perovskite (with a bandgap tuned to ≈1.2eV) is also attractive as the bottom subcell for a tandem configuration to further surpass the Shockley-Queisser radiative limit for the single-junction devices. The performance of the all-perovskite tandem solar cells has gained rapid development and achieved a certified efficiency up to 29.1%. In this article, the properties and recent development of state-of-the-art mixed Sn-Pb perovskites and their application in single-junction and all-perovskite tandem solar cells are reviewed. Recent advances in various approaches covering additives, solvents, interfaces, and perovskite growth are highlighted. The authors also provide the perspective and outlook on the challenges and strategies for further development of mixed Sn-Pb perovskites in both efficiency and stability for PV applications.