Introduction

Perovskite solar cells have achieved remarkable efficiency gains, with recent records reaching 34.85 % for perovskite–silicon tandem devices and certified single-junction cells achieving 26.95 % power conversion efficiency. This rapid progress has positioned metal-halide perovskites as one of the most promising photovoltaic technologies for both standalone applications and tandem architectures with silicon. However, transitioning from laboratory-scale devices to commercially viable large-area modules presents significant challenges, particularly in thin-film deposition methods.

Physical vapour deposition (PVD) techniques, particularly thermal evaporation and related vacuum-based processes, offer compelling advantages for perovskite solar cell manufacturing. These methods provide solvent-free processing, precise thickness control, excellent reproducibility, and compatibility with industrial roll-to-roll production systems. This article examines the critical challenges in perovskite thin-film deposition and explores how advanced PVD systems address these obstacles while enabling scalable, high-performance solar cell production.

Understanding Perovskite Solar Cell Architecture

Metal-halide perovskite solar cells employ the ABX₃ crystal structure, where A represents an organic or inorganic cation (e.g. methylammonium MA⁺, formamidinium FA⁺, or caesium Cs⁺), B is typically lead (Pb²⁺), and X denotes halide ions (iodide I⁻, bromide Br⁻, or chloride Cl⁻). The most efficient compositions feature mixed cations and halides, such as FA₀.₈₃Cs₀.₁₇PbI₃ or FA₀.₇Cs₀.₃Pb(I₀.₉Br₀.₁)₃, which optimise bandgap, stability, and charge transport properties.

Standard device architectures include:

n–i–p (regular) configuration: Transparent conducting oxide / electron transport layer (ETL) / perovskite absorber / hole transport layer (HTL) / metal electrode

p–i–n (inverted) configuration: Transparent conducting oxide / HTL / perovskite absorber / ETL / metal electrode

Each layer requires precise control over thickness, morphology, composition, and interface quality to achieve optimal performance. The perovskite absorber layer, typically 300 – 600 nm thick, presents the most significant deposition challenges.

Critical Challenges in Perovskite Thin-Film Deposition

Solution Processing Limitations

Traditional solution-based methods like spin coating face significant scalability challenges including material waste, difficulty achieving uniform films over large areas, and toxic solvent usage. Dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), the most common perovskite solvents, present environmental and health concerns at production scales.

Key issues with solution processing include:

Uniformity challenges: Film thickness and composition variations across large substrates lead to performance inconsistencies. Crystallisation kinetics during solvent evaporation create morphological defects that act as recombination centres limiting the efficiency of charge transfer through the cell.

Limited multilayer compatibility: Subsequent solution depositions can dissolve or damage underlying perovskite layers, complicating multi-junction device fabrication and tandem cell integration.

Batch-to-batch variability: Solution aging, atmospheric moisture sensitivity, and processing window constraints create reproducibility challenges unsuitable for mass manufacturing.

Environmental concerns: Toxic solvents used in perovskite processing create hazardous waste streams and require specialised handling on production lines.

Material Stability and Degradation: Perovskite materials exhibit inherent stability challenges that complicate processing:

Thermal sensitivity: Many perovskite compositions degrade at temperatures above 100 °C, limiting processing options and packaging methods. The volatile nature of organic cations (particularly methylammonium) leads to composition changes during heating.

Moisture susceptibility: Perovskite films readily degrade in humid environments, forming lead iodide and losing photovoltaic function. Processing in controlled atmospheres increases manufacturing complexity and cost.

Phase instability: Formamidinium cations have a large ionic radius and so formamidinium-based perovskites with Goldschmidt tolerance factors above 1.0, such as FAPbI₃, can transform into undesirable hexagonal phases, particularly under thermal or environmental stress.

Interface Engineering Complexity: Device performance depends critically on interfaces between the perovskite absorber and charge transport layers, where energy barriers, recombination losses, and adhesion failures significantly impact efficiency. Solution-processed interfaces often suffer from incomplete coverage, interdiffusion, and chemical reactions between layers.

Scalability Barriers: Laboratory devices achieving record efficiencies typically measure less than 0.1 cm², while commercial modules require areas exceeding 100 cm². This four-order-of-magnitude scale-up introduces:

• Thickness uniformity requirements across large areas
• Edge effects and composition gradients
• Increased defect density and shunt pathways
• Mechanical stress and delamination risks
• Throughput limitations of batch processes

Physical Vapour Deposition: Fundamentals and Advantages

PVD encompasses techniques where materials transfer from source to substrate via the vapour phase under vacuum conditions. For the perovskite layer in perovskite solar cells, thermal evaporation represents the primary PVD approach, offering distinct advantages over solution methods.

Thermal Evaporation Techniques

Co-evaporation (simultaneous deposition): Multiple precursors sublimate simultaneously from separate sources, before depositing on substrates. This approach enables real-time composition control through independent source temperature management.

Sequential evaporation (layer-by-layer): Precursors deposit separately in sequential steps, avoiding cross-contamination by processing materials in different chambers or time periods. Recent advances have demonstrated over 24 % efficiency using chloride-alloyed sequential deposition.

Hybrid methods: Combining thermal evaporation with chemical vapour deposition (CVD), gas-solid reactions, or solution processing leverages advantages of multiple techniques while mitigating individual limitations.

Core Advantages of PVD for Perovskites

Solvent-free processing: Eliminating toxic organic solvents addresses environmental concerns, simplifies safety requirements, and removes solvent-related defects from film formation.

Precise thickness control: Quartz crystal microbalances and optical monitoring enable angstrom-level control over deposition rates and film thickness, critical for optimising light absorption and charge extraction.

Excellent reproducibility: Vacuum environments provide cleaner deposition environments and eliminate atmospheric variables, while temperature and rate controls ensure consistent film properties batch-to-batch. This reproducibility proves essential for manufacturing.

Superior uniformity: Properly designed evaporation systems achieve thickness variations under 3 % across substrate areas exceeding 100 cm², far superior to solution coating methods.

Multi-layer compatibility: Sequential vacuum depositions avoid solvent damage to underlying layers, enabling complex multilayer architectures including tandem cells and advanced interface engineering.

Scalability potential: Thermal evaporation technology already implemented in OLED and semiconductor industries provides proven pathways for high-throughput manufacturing.

Process cleanliness: High-vacuum conditions minimise contamination from atmospheric species, resulting in purer films with fewer defect states.

Technical Challenges in PVD of Perovskites

Despite significant advantages, PVD of perovskite films presents unique technical challenges requiring sophisticated equipment and process optimisation.

Organic Precursor Volatility: Organic cations like methylammonium iodide exhibit high volatility, low molecular mass, and low sticking coefficients on many substrates, making deposition rate control extremely difficult. MAI tends to re-evaporate from substrates during deposition, creating stoichiometry variations.

Formamidinium advantages: FA-based perovskites demonstrate improved thermal stability compared to MA compositions, but FAI also presents volatility challenges during evaporation. Researchers have observed FAI material degradation during thermal evaporation, forming unwanted decomposition products.

Stoichiometry Control: Achieving the precise composition ratio between organic and inorganic precursors proves critical for phase purity and device performance. Slight deviations create:

• Non-perovskite phases (e.g., hexagonal δ-phase)
• Lead iodide excess or deficiency
• Trap states from compositional defects
• Bandgap variations affecting light absorption

Solution approach: Controlled addition of excess PbI₂ (typically 5 – 10 %) during deposition improves performance and stability by compensating for organic cation loss and passivating defects.

Deposition Rate Optimisation: Perovskite film quality depends sensitively on deposition rate. Too rapid deposition prevents proper crystallisation, while excessively slow rates increase process time and allow substrate heating effects.

Conventional thermal evaporation achieves rates around 0.1 – 1 nm s⁻¹, but recent high-speed vapour transport techniques demonstrate rates exceeding 1 nm s⁻¹ while maintaining film quality.

Substrate Temperature Management: Unlike many PVD applications, where elevated substrate temperatures enhance film quality, perovskite depositions often require moderate temperatures:

Ambient to 50 °C: Prevents premature thermal degradation while allowing sufficient atomic mobility for crystallisation. However, low temperatures may limit grain growth and film densification.

Temperature uniformity: Large substrates require precise temperature control across entire areas to ensure consistent film properties.

Phase Formation and Crystallisation: Forming highly crystalline perovskite films with correct phases requires precise control of deposition parameters in vacuum co-deposition. Post-deposition annealing often proves necessary to complete crystallisation and optimise grain structure but must balance between promoting grain growth and avoiding thermal degradation.

Multi-source Coordination: Evaporating complex multi-cation, multi-halide compositions requires simultaneous control of four or more sources. Each source operates at different temperatures (100 – 350 °C range) with independent rate controls, demanding sophisticated process management.

Advanced PVD System Requirements for Perovskite Research

Successfully depositing high-quality perovskite films requires PVD systems specifically designed or adapted for these materials’ unique properties.

Essential System Specifications

Multi-source capability: Minimum four independent thermal evaporation sources to accommodate:

• Lead halides (PbI₂, PbBr₂, PbCl₂)
• Alkali halides (CsI, CsBr)
• Organic cations (MAI, FAI)
• Dopants and additives

Precise temperature control: Each source requires independent temperature control with ±1 °C stability across 100 – 400 °C range. Substrate temperature control from ambient to 150 °C with similar precision.

Deposition rate monitoring: Quartz crystal microbalance (QCM) sensors positioned for each source, calibrated for the specific precursor materials. Typical rate ranges: 0.1 – 2 Å s⁻¹.

Vacuum system performance:

• Base pressure: 10⁻⁶ mbar or better (high vacuum)
• Working pressure during deposition: 10⁻⁵ to 10⁻⁴ mbar
• Fast pump-down capability to minimise substrate exposure time

Substrate manipulation:

• Rotation for improved uniformity (typical: 10 – 30 rpm)
• Heating capability with uniform temperature distribution
• Shutter systems for source pre-conditioning and precise deposition timing
• Sufficient source-to-substrate distance (typically 15 – 25 cm) for uniform coverage

Process control automation:

• Recipe storage for reproducible multi-step depositions
• Real-time rate and temperature feedback loops
• Data logging for quality control and troubleshooting
• Interlock systems preventing cross-contamination

Chamber Design Considerations

Source configuration: Confocal arrangement with sources angled toward substrate centre optimises uniformity. Alternatively, linear sources suit larger substrate geometries.

Contamination prevention: Separate chambers or load-lock systems prevent atmospheric exposure during sample transfer, critical given perovskite moisture sensitivity.

Material compatibility: Internal surfaces should resist perovskite precursor reactions. Stainless steel construction with removable shields facilitates cleaning and maintenance.

Viewport access: Multiple viewports enable process observation and potential integration of in-situ diagnostic tools.

Advanced Monitoring and Control

Optical thickness monitoring: Real-time ellipsometry or reflectometry provides additional verification of film thickness and optical properties during growth.

Mass spectrometry: Residual gas analysers (RGA) detect chamber contamination, monitor precursor vapour partial pressures, and identify decomposition products.

Temperature mapping: Multi-point substrate temperature measurement ensures uniformity across large areas.

Automated recipe control: Pre-programmed sequences manage complex multi-step depositions including pre-conditioning, layer-by-layer depositions, and co-evaporation phases.

Benchtop PVD Solutions for Perovskite Research

Modern benchtop PVD systems specifically configured for perovskite research offer capabilities previously available only in large industrial systems.

Compact Multi-Source Evaporation Systems

Research-scale systems (chamber volume 40 – 80 litres): Accommodate substrates up to 150 mm/6 inches while maintaining benchtop footprint. Typical configurations include:

• 4 – 6 independently controlled thermal evaporation sources
• Substrate rotation and heating to 200 °C
• Individual QCM sensors per source
• Base pressure 10⁻⁶ mbar with turbomolecular pumping
• Manual or automated shutter control
• Recipe storage and data logging

Sequential Deposition Systems

Optimised for layer-by-layer perovskite fabrication, these systems feature:

• Separate evaporation zones or chambers, preventing cross-contamination
• Automated substrate transfer between deposition stages
• Independent atmosphere control per chamber
• Integration with post-deposition annealing systems

These configurations particularly suit research into FA-based perovskites and novel composition optimisation.

Hybrid Systems

Combining PVD with complementary techniques addresses specific challenges:

PVD + CVD integration: Thermal evaporation of lead halide layers followed by gas-phase conversion using organic halide vapours. This hybrid approach can achieve high-quality films while simplifying process control.

PVD + solution processing: Some laboratories successfully combine evaporated base layers with solution-processed top layers or interface materials, leveraging strengths of both methods.

Best Practices for Perovskite PVD Processing

Source Material Selection and Preparation

Purity requirements: Use 99.99 % (4N) or higher purity precursors to minimise impurity-related defects. Lead halides and organic cations should be stored under inert atmosphere to prevent hydration.

Source loading: Load crucibles in a glove box or dry nitrogen environment. Preheat sources under vacuum to remove residual moisture before deposition.

Material conditioning: Allow sources to reach stable sublimation temperature while shutters closed. This pre-conditioning ensures consistent rate when deposition begins.

Process Optimisation Strategies

Rate calibration: Calibrate QCM sensors for each precursor material using known film thickness measurements (profilometry, ellipsometry). Tooling factors vary significantly between materials.

Temperature mapping: Characterise substrate temperature uniformity using thermocouples or infrared imaging before processing actual samples. Adjust heating element positions or add thermal shields to improve uniformity.

Composition optimisation: Systematic variation of precursor ratios, particularly excess PbI₂ content, dramatically impacts device performance. Start with literature-reported ratios then optimise for your specific system.

Annealing protocols: Post-deposition annealing typically required for optimal crystallinity. Explore temperature (50 – 150 °C), time (5 – 60 minutes), and atmosphere (vacuum, nitrogen, air) combinations.

Contamination Control

Dedicated systems: Reserve PVD systems exclusively for perovskite research when possible. Lead-containing materials can contaminate systems, affecting other experiments.

Regular cleaning: Remove source shields and clean chamber walls monthly to prevent buildup interfering with deposition uniformity.

Moisture management: Even in vacuum, residual moisture affects perovskite film formation. Thorough baking of chambers and extended pump-down times prove beneficial.

Recent Advances and Future Directions

All-Vacuum Device Fabrication

Researchers have demonstrated fully evaporated perovskite solar cells achieving 13.9 % efficiency with excellent long-term stability, showing no degradation after over 3,700 hours at 85 °C. These devices eliminate solution-processed charge transport layers, simplifying manufacturing and improving thermal stability.

High-Efficiency Vacuum-Deposited Cells

Recent chloride-alloyed sequential vacuum deposition methods have achieved certified efficiencies exceeding 24 %, approaching the performance of best solution-processed devices. This progress demonstrates vacuum deposition as a viable route for high-performance perovskite photovoltaics.

Large-Area Modules

Industry efforts focus on scaling vacuum-deposited perovskites to module sizes. Companies like Oxford PV have shipped tandem perovskite-silicon modules with 24.5 % efficiency to commercial installations, with plans for gigawatt-scale production.

Tandem Cell Integration

Perovskite-silicon tandem architectures theoretically enable up to 43 % efficiency, far exceeding single-junction limits. Vacuum deposition’s compatibility with silicon processing and multilayer fabrication makes it particularly attractive for tandem development.

Methylammonium-Free Compositions

To address MA volatility and stability concerns, research increasingly focuses on FA/Cs mixed-cation perovskites deposited entirely by thermal evaporation. Multi-source vacuum deposition of MA-free compositions like FA₀.₇Cs₀.₃Pb(I₀.₉Br₀.₁)₃ has achieved stabilised power outputs of 18.2 % with improved thermal stability.

Lead-Free Alternatives

Environmental concerns about lead toxicity drive research into tin-, germanium-, and bismuth-based perovskites. Vacuum deposition proves particularly valuable for these alternative compositions, many of which exhibit greater air sensitivity than lead perovskites.

In-Situ Monitoring and Control

Integration of real-time diagnostic tools promises improved process control:

• X-ray diffraction monitoring phase evolution during deposition
• Photoluminescence spectroscopy assessing optoelectronic quality
• Reflectometry tracking optical properties in real time

These techniques enable feedback control loops optimising film properties during growth rather than through post-deposition characterisation.

Atmospheric Pressure Techniques

High-speed vapour transport at elevated pressures (around 10 mbar) has demonstrated deposition rates exceeding 1 nm s⁻¹, potentially bridging the gap between high vacuum and atmospheric processing while maintaining vapour-phase advantages.

Selecting PVD Equipment for Perovskite Research

Defining Research Objectives

Material exploration: Systems with maximum source flexibility (6+ sources) enable investigation of novel compositions including multiple cations, mixed halides, and additives.

Device optimisation: Standard 4-source configurations suffice for optimising well-established compositions like FA/Cs mixed-cation perovskites.

Scale-up research: Larger chambers (100+ litre volume) with enhanced uniformity prove necessary for module development and manufacturing process translation.

System Configuration Recommendations

For academic research groups:

• Chamber volume: 40 – 60 litres (100 – 150-mm/4 – 6-inch substrate capacity)
• Four thermal evaporation sources minimum
• Individual QCM per source
• Substrate heating to 150 °C with rotation
• Base pressure: 10⁻⁶ mbar
• Budget: £60,000 – £90,000

For advanced materials research:

• Chamber volume: 60 – 200 litres
• Six thermal evaporation sources
• Load-lock for atmospheric isolation
• Advanced process control with recipe automation
• In-situ optical monitoring capability
• Budget: £90,000 – £140,000+

For industrial prototyping:

• Large-area chamber (substrate > 250 mm/10 inches)
• Multi-substrate capability or continuous processing
• Full automation with high throughput
• Comprehensive monitoring and quality control
• Budget: £150,000 – £300,000+

Key Supplier Evaluation Criteria

Technical expertise: Does the supplier understand perovskite-specific requirements? Can they provide application support for process development?

Source design: Are evaporation sources suitable for organic materials (low thermal mass, precise temperature control)? Can they handle material sublimation characteristics?

Customisation capability: Will the supplier adapt standard systems for perovskite applications or offer only fixed configurations?

Training and support: Comprehensive operator training proves essential given process complexity. Assess ongoing technical support quality and response times.

Upgrade pathways: Can the system accommodate additional sources, monitoring equipment, or automation as research progresses?

Case Studies: PVD in Perovskite Research

University Research Laboratory Implementation

A UK materials science department invested £85,000 in a benchtop multi-source evaporation system configured for perovskite research. The system features:

• Four independently controlled thermal sources
• 50-litre chamber accommodating 4-inch substrates
• Substrate rotation and heating to 200 °C
• QCM monitoring for each source
• Automated shutter control and recipe storage

Results after two years:

• Optimised FA₀.₈₃Cs₀.₁₇PbI₃ deposition achieving 19 % device efficiency
• Investigated ten novel compositions including tin-based alternatives
• Trained 12 PhD and postdoctoral researchers
• Published eight peer-reviewed papers
• Secured £450,000 in follow-on research funding
• Established industry collaboration for scale-up research

The laboratory calculated that eliminating outsourced thin-film services (previously £2,000+ monthly) provided payback within 18 months while enabling research impossible with external processing.

Industrial R&D Facility

A solar technology company developing perovskite–silicon tandem cells invested £280,000 in a large-area PVD system for pilot-line development. Key specifications:

• 150-litre chamber processing 6-inch wafers
• Six thermal evaporation sources with individual control
• Load-lock system for atmospheric isolation
• Full automation with integrated annealing
• Comprehensive in-situ monitoring

The system enabled successful tandem cell prototyping achieving 28 % efficiency and demonstrated compatibility with silicon processing infrastructure, positioning the company for commercial product development.

Environmental and Safety Considerations

Advantages of PVD Processing

Solvent elimination: Vacuum deposition avoids toxic organic solvents entirely, eliminating hazardous waste streams and reducing environmental impact significantly.

Reduced chemical handling: Solid precursor materials prove safer to store and handle than liquid solutions, with lower volatility and easier containment.

Controlled atmospheres: Processing in vacuum or inert gas eliminates atmospheric contamination while enabling complete exhaust gas capture and treatment.

Safety Requirements

Lead handling: Despite vacuum processing, lead-containing materials require appropriate precautions:

• Designated handling areas with proper ventilation
• Personal protective equipment including respirators during source loading
• Regular air quality monitoring
• Waste disposal through certified hazardous waste contractors

Electrical hazards: High-temperature sources and substrate heaters require proper interlocks and shielding.

Vacuum safety: Large vacuum chambers present implosion risks; proper safety shields and pressure monitoring prove essential.

Thermal hazards: Sources operating at 300+ °C require cool-down periods and warning systems preventing accidental contact.

Return on Investment

Research laboratories typically achieve positive ROI within 2 – 3 years through:

• Eliminated outsourcing costs for thin-film deposition
• Enhanced research productivity enabling more rapid publication
• Improved grant competitiveness through in-house capabilities
• Industry collaboration opportunities leveraging unique equipment

For industrial R&D, payback periods depend on product development timelines but generally justify investment within prototype development phase.

Future Outlook

The field of vacuum-deposited perovskite solar cells continues rapid advancement, driven by both fundamental materials research and industrial scale-up efforts. Key trends include:

Commercialisation acceleration: Multiple companies have announced commercial perovskite products, with Oxford PV shipping panels and targeting gigawatt-scale production.

Efficiency improvements: Ongoing optimisation of vacuum deposition parameters, composition engineering, and interface design continues pushing efficiency toward theoretical limits.

Stability breakthroughs: Recent research demonstrates perovskite cells maintaining over 80% efficiency for 1,000+ hours under demanding conditions, addressing long-standing durability concerns.

Manufacturing readiness: Vacuum thermal evaporation’s compatibility with existing semiconductor manufacturing infrastructure positions it favourably for rapid industrial adoption.

Conclusion

Physical vapour deposition, particularly thermal evaporation, offers a compelling solution to critical challenges in perovskite solar cell development and manufacturing. By eliminating toxic solvents, enabling precise process control, and providing excellent reproducibility and scalability, PVD techniques address many limitations of solution-based methods.

While technical challenges remain, including organic precursor volatility, stoichiometry control, and process optimisation, modern benchtop PVD systems configured specifically for perovskite research provide researchers with the tools necessary to overcome these obstacles. Recent achievements of all-vacuum devices approaching 25 % efficiency for single cell architectures demonstrate the technology’s maturity and commercial viability.

For research laboratories investigating next-generation photovoltaics, investment in PVD capability provides access to cutting-edge perovskite solar cell development while building expertise in manufacturing-relevant processing techniques. As the field transitions from laboratory curiosity to commercial reality, vacuum deposition stands positioned as a key enabling technology for high-performance, scalable perovskite photovoltaics.

The convergence of improving efficiencies, enhanced stability, and manufacturing readiness suggests perovskite solar cells deposited by PVD will play an increasingly important role in the global renewable energy landscape. Research groups and companies equipped with appropriate PVD systems will be well-positioned to contribute to and benefit from this transformation.

References and Further Reading

1. Li, H., Zhou, J., Tan, L., Li, M., Jiang, C., Wang, S., Zhao, X., Liu, Y., Zhang, Y., Ye, Y. & Tress, W. Sequential vacuum-evaporated perovskite solar cells with more than 24% efficiency. Science advances 8(28), eabo7422 (2022). https://doi.org/10.1126/sciadv.abo7422
2. Jiang, Y., He, S., Qiu, L., Zhao, Y. & Qi, Y. Perovskite solar cells by vapor deposition based and assisted methods. Applied Physics Reviews 9(2) 021305 (2022). https://doi.org/10.1063/5.0085221
3. Lee, J.H., Kim, B.S., Park, J., Lee, J.W. & Kim, K. Opportunities and challenges for perovskite solar cells based on vacuum thermal evaporation. Advanced Materials Technologies 8(20), 2200928 (2023).
4. Yuan, Q., Lohmann, K.B., Oliver, R.D., Ramadan, A.J., Yan, S., Ball, J.M., Christoforo, M.G., Noel, N.K., Snaith, H.J., Herz, L.M. & Johnston, M.B. Thermally stable perovskite solar cells by all-vacuum deposition. ACS Applied Materials & Interfaces, 15(1), 772–781 (2023). https://doi.org/10.1021/acsami.2c14658
5. Abzieher, T., Moore, D.T., Roß, M., Albrecht, S., Silvia, J., Tan, H., Jeangros, Q., Ballif, C., Hoerantner, M.T., Kim, B.S. & Bolink, H.J. Vapor phase deposition of perovskite photovoltaics: short track to commercialization?. Energy & Environmental Science, 17(5), 1645–1663 (2024). https://doi.org/10.1039/D3EE03273F
6. Nie, R., Dai, Y., Wang, R., Li, L., Park, B.W., Chu, W., Wang, C., Li, Z., Chen, S., Qiao, R. & Yin, L. Enhanced stability and efficiency in perovskite solar cells via mixed-metal chalcohalide-alloyed formamidinium lead iodide. Nature Communications, 16(1), 7343 (2025). https://doi.org/10.1038/s41467-025-62125-x
7. American Ceramic Society (2025). Perovskite solar cells: Progress continues in efficiency, durability, and commercialization. Ceramic Tech Today. https://ceramics.org/ceramic-tech-today/perovskite-solar-cells-progress-2025/
8. Du, P., Wang, L., Li, J., Luo, J., Ma, Y., Tang, J. & Zhai, T. Thermal evaporation for halide perovskite optoelectronics: fundamentals, progress, and outlook. Advanced Optical Materials, 10(4), 2101770 (2022). https://doi.org/10.1002/adom.202101770
9. Gil-Escrig, L., Ross, M., Sutter, J., Al-Ashouri, A., Becker, C. & Albrecht, S. Fully vacuum‐processed perovskite solar cells on pyramidal microtextures. Solar RRL, 5(1), 2000553 (2021). https://doi.org/10.1002/solr.202000553
10. National Laboratory of the Rockies (NLR) formerly National Renewable Energy Laboratory (NREL) (2026). Interactive Best Research-Cell Efficiency Chart. https://www.nrel.gov/pv/cell-efficiency.html