Perovskite Tandem Solar Cells

Current State

Perovskite tandem solar cells, particularly perovskite/silicon tandems, are a leading candidate for next-generation photovoltaics, offering the potential to significantly increase power conversion efficiency (PCE) at an affordable cost (Aydın et al., 2024). All-perovskite tandem cells also show great promise. Recent advancements have pushed laboratory-scale efficiencies, with a strong emphasis on interface engineering and defect passivation to minimize recombination losses and improve stability.

Strongest Evidence

Significant progress has been made in addressing key challenges. Surface chemical polishing and passivation strategies, for instance, have been shown to effectively minimize non-radiative recombination in Sn–Pb mixed narrow bandgap perovskite films, crucial for all-perovskite tandems (Pan et al., 2024). Similarly, surface reconstruction methods, involving nano-polishing and subsequent passivation, have enabled efficient wide-bandgap (WBG) perovskite/silicon tandem solar cells by mitigating interfacial carrier loss and phase segregation (Fang et al., 2024). Compositional texture engineering has also been demonstrated to improve the stability of WBG perovskite solar cells, particularly against bromine-iodine phase segregation under operational conditions (Jiang et al., 2022). Self-assembled monolayers (SAMs) are increasingly recognized for their role in manipulating chemical and physical interface properties, leading to improved efficiency and stability in both single-junction and tandem configurations (Yi et al., 2024).

Unresolved Uncertainties

Despite these advances, challenges remain. Light-induced halide segregation continues to constrain the performance and stability of WBG perovskite solar cells and tandem cells (Wen et al., 2023). While strategies like intermixed 2D/3D heterostructures are explored, their effectiveness is often composition-dependent, requiring further optimization. The long-term operational stability under real-world conditions, particularly for large-area devices, is still a critical area of research. Scaling up laboratory-scale successes to commercial production also presents manufacturing and cost challenges.

Why the Topic Matters

Perovskite tandem solar cells are crucial for pushing the boundaries of photovoltaic efficiency beyond the Shockley–Queisser limit of single-junction cells. By achieving higher efficiencies at potentially lower costs, this technology can accelerate the transition to sustainable energy, reduce the land footprint required for solar farms, and enhance the overall economic viability of solar power. Addressing the remaining stability and scalability issues is paramount for their widespread commercial adoption.

Points of Agreement

• Perovskite/silicon tandem solar cells offer a promising route to surpass the theoretical efficiency limits of single-junction silicon solar cells at an affordable cost, with significant progress in laboratory-scale efficiencies. (Aydın et al., 2024)
• Interface engineering and defect passivation are crucial for minimizing non-radiative recombination losses and improving the performance and stability of both wide-bandgap (WBG) and narrow-bandgap perovskite films in tandem devices. (Pan et al., 2024; Fang et al., 2024)
• Self-assembled monolayers (SAMs) are highly effective in manipulating chemical and physical interface properties in inverted perovskite solar cells, leading to improved efficiency and stability in tandem configurations. (Yi et al., 2024)
• Halide segregation, particularly in bromine-iodine mixed-halide WBG perovskites, is a major challenge limiting device voltage and operational stability, often exacerbated by rapid crystallization and defect formation. (Jiang et al., 2022; Wen et al., 2023)

Active Disagreements

• There is ongoing debate regarding the optimal processing technologies (vacuum- vs. solution-based) for perovskite layers in commercial-scale tandem fabrication, with each having distinct advantages and challenges in terms of scalability and cost. (Aydın et al., 2024)
• The most effective strategies for mitigating halide segregation in WBG perovskites are still under active investigation, with approaches ranging from compositional texture engineering to 3D-to-2D perovskite conversion and surface reconstruction methods. (Jiang et al., 2022; Wen et al., 2023; Fang et al., 2024)

Uncertain Claims

• The long-term stability and degradation mechanisms of perovskite tandem solar cells under various environmental stressors (e.g., heat, humidity, continuous illumination) are not yet fully understood, particularly for commercial applications. (Aydın et al., 2024)
• The precise impact of different surface reconstruction and passivation agents on the long-term performance and reliability of perovskite films in tandem structures requires further comprehensive evaluation. (Pan et al., 2024; Fang et al., 2024)

Evidence Gaps

• Limited data exists on the performance and cost-effectiveness of perovskite tandem solar cells at a manufacturing scale, beyond laboratory prototypes. (Aydın et al., 2024)
• There is a lack of standardized testing protocols and long-term outdoor performance data for various perovskite tandem architectures, making direct comparisons and commercial viability assessments challenging. (Aydın et al., 2024)
• More research is needed to fully understand the fundamental mechanisms of defect formation and carrier dynamics at complex interfaces within multi-junction perovskite tandem devices. (Pan et al., 2024; Fang et al., 2024)

Claim 1: Perovskite/silicon tandem solar cells offer a promising route to increase power conversion efficiency (PCE) beyond single-junction limitations.

• Supporting Evidence: A review by Aydın et al. (2024) highlights the progress in fabricating highly efficient laboratory-scale perovskite/silicon tandems, emphasizing their potential for affordable efficiency gains. This claim is strongly supported.
• Limitations: While laboratory efficiencies are high, scaling these to commercial production with comparable performance and cost-effectiveness remains a challenge.

Claim 2: Surface and interface engineering are critical for minimizing non-radiative recombination and improving the efficiency and stability of perovskite tandem solar cells.

• Supporting Evidence: Pan et al. (2024) demonstrate a surface reconstruction strategy using 1,4-butanediamine to minimize non-radiative recombination in all-perovskite tandem solar cells, leading to improved performance. Fang et al. (2024) also show that nano-polishing and passivation of wide-bandgap perovskite surfaces reduce defects and improve tandem cell efficiency. Yi et al. (2024) review the significant progress achieved by self-assembled monolayers (SAMs) in manipulating interface properties for both efficiency and stability in inverted perovskite solar cells and their tandem applications. This evidence is strong and consistent across multiple studies.
• Limitations: The long-term stability of these engineered interfaces under various operational conditions still requires extensive validation, especially for commercial applications.

Claim 3: Wide-bandgap (WBG) perovskites, crucial for tandem solar cells, face stability challenges due to phase segregation and defect formation.

• Supporting Evidence: Jiang et al. (2022) address the issues of bromine-iodine (Br–I) phase segregation and defect formation in WBG perovskites under operational conditions, which limit device voltage and stability. Fang et al. (2024) also identify defect-rich surfaces in WBG-PSCs as a cause of severe interfacial carrier loss and phase segregation. This claim is strongly supported.
• Limitations: While solutions like compositional texture engineering (Jiang et al., 2022) and surface reconstruction (Fang et al., 2024) are being developed, completely overcoming these inherent material challenges for long-term stability remains an active research area.

Recent advancements in perovskite tandem solar cells highlight a strong push towards enhanced power conversion efficiency (PCE) and improved stability, critical for their commercialization. All-perovskite tandem solar cells are showing promise in surpassing the Shockley–Queisser limit of single-junction devices. A key trend involves sophisticated interface engineering, such as surface chemical polishing and passivation techniques, to significantly reduce non-radiative recombination losses, which are a major hindrance to efficiency improvements (Pan et al., 2024).

Another significant trend is the focus on compositional texture engineering, particularly for wide-bandgap (WBG) perovskite solar cells. These WBG cells, often based on bromine-iodine mixed-halide perovskites, are essential components in tandem architectures. Addressing issues like Br–I phase segregation through texture engineering is crucial for achieving highly stable WBG perovskite solar cells, thereby improving the overall stability of tandem devices (Jiang et al., 2022).

Furthermore, the broader landscape of perovskite/silicon tandem photovoltaics is seeing concerted efforts to identify and overcome barriers to commercialization. This includes not only efficiency gains but also a deep dive into understanding degradation mechanisms and developing strategies to enhance long-term operational stability at an affordable cost (Aydın et al., 2024). These trends collectively indicate a maturing field moving from fundamental research to practical, market-ready solutions.

Synthesis

Perovskite tandem solar cells, particularly perovskite/silicon and all-perovskite configurations, are advancing toward surpassing the Shockley-Queisser limit of single-junction cells. The primary focus is on improving the wide-bandgap (WBG) perovskite top cell, which is critical for overall tandem performance and stability. Research highlights the mitigation of non-radiative recombination losses caused by surface defects and halide segregation under operational stress. Strategies like surface reconstruction, compositional engineering, and advanced interface layers are proving effective in boosting both efficiency and device longevity, moving the technology closer to commercial viability.

Methods & Materials

Key methods involve sophisticated interface and material engineering. Surface reconstruction techniques, such as chemical polishing and passivation, are used to remove defect-rich surfaces and passivate newly exposed, high-crystallinity layers, thereby reducing non-radiative recombination (Pan et al., 2024; Fang et al., 2024). Compositional engineering employs additives, like chlorides or anion-engineered 2D additives, to control crystallization, suppress halide segregation, and improve stability in WBG perovskites (Shen et al., 2023; Kim et al., 2020). Self-assembled monolayers (SAMs) are increasingly used as hole-transport layers in inverted cell architectures to optimize energy level alignment and passivate defects at the interface, benefiting both single-junction and tandem devices (Yi et al., 2024). Additionally, techniques like gentle gas-quenching are being combined with compositional tuning to create highly textured perovskite films with enhanced stability (Jiang et al., 2022).

Applications

Perovskite tandem solar cells are primarily aimed at high-efficiency photovoltaic applications. The most prominent application is in perovskite/silicon tandem cells, which leverage the established silicon solar industry infrastructure to create cells with efficiencies exceeding 30% (Aydın et al., 2024). All-perovskite tandem cells offer a pathway to lightweight, flexible, and low-cost solar modules, although they are at an earlier stage of development. The successful commercialization of these technologies could significantly lower the levelized cost of electricity and expand the applications of solar power.

Limitations

Despite rapid progress, significant challenges remain. Operational stability is the primary barrier; WBG perovskites suffer from light- and heat-induced halide segregation, which degrades performance over time (Jiang et al., 2022; Wen et al., 2023). Scalability of the advanced laboratory techniques to industrial-scale manufacturing is another major hurdle, requiring the development of scalable materials and processes (Aydın et al., 2024). Furthermore, the open-circuit voltage (Voc) deficit in WBG cells still limits the maximum achievable efficiency, and defects in narrow-bandgap Sn-Pb perovskites hinder the progress of all-perovskite tandems (Pan et al., 2024).

Update Triggers

This review should be updated upon the publication of new research demonstrating:

1. Certified tandem cell efficiencies surpassing current world records.
2. Novel passivation or compositional engineering strategies that result in substantial improvements in the operational stability (e.g., passing IEC 61215 stress tests).
3. Breakthroughs in scalable deposition techniques for high-quality perovskite layers suitable for commercial production.
4. Significant reduction in the Voc deficit of WBG cells or improved stability of Sn-Pb perovskite bottom cells for all-perovskite tandems.

Near-Term Work

1. Interface Engineering & Defect Passivation: Focus on developing and optimizing novel self-assembled monolayers (SAMs) and surface treatments for both perovskite/silicon and all-perovskite tandems. The goal is to minimize non-radiative recombination losses at interfaces, particularly in Sn-Pb narrow-bandgap subcells, as demonstrated by surface chemical polishing techniques.
2. Wide-Bandgap (WBG) Perovskite Stability: Investigate advanced compositional engineering strategies, such as "compositional texture engineering," to suppress halide phase segregation in Br-rich WBG top cells under operational stress (light, heat). This is crucial for maintaining high open-circuit voltage (Voc) and long-term stability.
3. Scalable Fabrication: Develop and refine scalable deposition methods (e.g., slot-die coating, vapor deposition) for uniform, large-area perovskite layers and interconnects. Research must address the transition from lab-scale spin-coating to commercially viable manufacturing processes.

Validation Needs & Benchmarks

• Standardized Stability Testing: Establish universally accepted protocols for long-term stability assessment, including damp-heat (IEC 61215), thermal cycling, and maximum power point tracking under continuous illumination. This is a primary barrier to commercial adoption.
• Performance Benchmarks: Continue tracking and validating certified power conversion efficiency (PCE) for various architectures (2T, 4T, perovskite/silicon, all-perovskite). Key metrics include certified stabilized efficiency, Voc, fill factor, and energy yield modeling for specific climates.

High-Value Experiments

• Encapsulation & Module Integration: Conduct experiments on advanced, low-cost encapsulation materials and techniques that prevent moisture/oxygen ingress without degrading the perovskite layers. Fabricate and test mini-modules to identify and solve integration challenges.
• In-situ Characterization: Employ in-situ/operando characterization techniques (e.g., PL, XRD) to monitor phase segregation and degradation pathways in WBG cells under real-time operational stress, providing direct feedback for materials design.

Translation Barriers

• Long-Term Operational Stability: The primary barrier is achieving 25+ year stability required for commercial bankability.
• Scalability & Cost: Developing low-cost, high-throughput manufacturing processes for large-area modules remains a significant challenge.
• Lead (Pb) Toxicity: Public perception and environmental regulations regarding lead content require robust encapsulation solutions and research into lead-free alternatives.