Organic-inorganic hybrid perovskite solar cells (PeSCs) are a promising next-generation photovoltaic (PV) technology with a demonstrated power conversion efficiency (PCE) of 26.1%. Despite record efficiencies rivaling crystalline Si PV (26.8% PCE), several challenges hinder real-world applications. The most significant is translating small-area lab-scale cells, often fabricated using economically unviable methods, into large-area devices produced via high-volume, low-cost manufacturing. High PCE technologies like inorganic multi-junction or GaAs cells demonstrate that failure to reduce production costs prevents market penetration. PeSCs offer the potential for low-cost, low-energy manufacturing using solution-based industrial processes (spray, blade, and slot-die coating). Recent advances in large-area glass-based PeSCs show promising efficiencies (up to 25.8%), but these use discrete sheet-to-sheet processing, vacuum-based evaporation, and subtractive laser-patterning for interconnections, increasing production costs. Flexible PeSCs, using continuous roll-to-roll (R2R) manufacturing, offer higher volume and throughput. Their lightweight and flexibility also allow for high specific power, desirable for space, vehicle-integrated PV, and building-integrated PV applications. However, R2R processing on flexible plastic substrates presents challenges like time and temperature limitations. Beyond manufacturing, replacing high-cost components (e.g., vacuum-processed Au electrodes and transparent conductive electrodes (TCEs)) with cheaper alternatives while maintaining performance remains crucial. Vacuum deposition is expensive and incompatible with standard R2R lines. While solution-processed back electrodes have been reported in glass-based devices, their high-temperature processing is unsuitable for flexible substrates and R2R upscaling. A recent report (February 2023) showed the first small-area (0.09 cm²) PeSC with all layers deposited on a flexible plastic substrate using R2R, achieving up to 10.8% PCE. However, this efficiency is still far from that of typical research cells, and only small cells were demonstrated. This research addresses these limitations by presenting the fabrication of entirely R2R-printed individual PeSCs with a record-high 15.5% PCE and the first demonstration of PeSC modules fabricated using only industry-relevant R2R techniques under ambient room conditions.

The literature extensively covers perovskite solar cell research, highlighting the progress in achieving high power conversion efficiencies in laboratory settings. However, a significant gap exists in translating these laboratory-scale achievements to large-area, cost-effective manufacturing processes suitable for industrial applications. Several studies have explored various solution-based deposition techniques like spray coating, blade coating, and slot-die coating for large-area perovskite film deposition. While these methods have shown promise in achieving reasonably high efficiencies, they often involve steps that are not readily scalable or compatible with high-throughput roll-to-roll manufacturing. The use of vacuum deposition for electrode fabrication adds significant cost and complexity, limiting the scalability of the process. Recent efforts have focused on developing solution-processed electrodes, primarily carbon-based materials, as a potential alternative to vacuum-deposited metal electrodes. However, the performance of these solution-processed electrodes has generally lagged behind their vacuum-deposited counterparts, requiring further optimization for achieving comparable efficiencies in large-area devices. Furthermore, the development of roll-to-roll compatible fabrication techniques for perovskite solar cells is still an active area of research, with limited success in achieving both high efficiency and large-scale production. This study directly addresses these challenges by combining innovative processing techniques with a robust, scalable roll-to-roll manufacturing process to produce high-efficiency perovskite solar cell modules.

The researchers developed a comprehensive methodology encompassing several key innovations to achieve entirely roll-to-roll (R2R) fabricated perovskite solar cells and modules under ambient room conditions. Their approach involved three main components: (i) development of a robust and scalable deposition technique, (ii) creation of perovskite-friendly carbon inks to replace costly vacuum-deposited electrodes, and (iii) implementation of a R2R-based high-throughput experimental platform for rapid optimization. **Perovskite Crystallization Control:** The study utilized and improved a 'printing-friendly sequential deposition' (PFSD) technique, which involves adding organic cations at a low concentration to retard crystallization, improving film-forming properties. A crucial innovation was the introduction of 'shallow-angle blowing', a technique for applying a nitrogen gas flow across the substrate to improve film uniformity and reduce defects. This method was crucial for the scalability of the process. **Carbon Electrode Development:** To eliminate expensive vacuum-deposited metal electrodes, the researchers developed perovskite-friendly carbon inks. These inks were formulated using a combination of carbon black and graphene nanoplatelets, optimized for printability and electrical conductivity using a three-roll mill to break down pigment agglomerates. **High-Throughput R2R Platform:** The team developed a programmable R2R slot-die coater for automated, unmanned operation, allowing for high-throughput fabrication of thousands of unique PeSCs daily. An automated R2R tester was also created for automated testing of over ten thousand cells per day. This high-throughput platform enabled rapid exploration of fabrication parameters and optimization. The parameters involved included different thicknesses and stoichiometries of the perovskite film, along with different hole-transport layers (HTLs) and the incorporation of printed silver grids in modules. The HTL system using Poly(3-hexylthiophene) (P3HT) with n-hexyl trimethyl ammonium bromide (HTAB) was optimized for R2R processing by carefully controlling surface reactivity and using substrate heating. **Module Fabrication:** The optimized fabrication parameters were then used to produce large-area modules. Slot-die coating heads with multiple channels were used to deposit stripes of materials for the individual cells, with screen printing used to deposit silver grids for charge collection and cell interconnection. **Characterization:** A range of characterization techniques were employed to assess the properties of the materials and devices, including J-V measurements (manual and automated), incident photon-to-current efficiency (IPCE) measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), and time-resolved photoluminescence measurements.

This study reports several significant findings: 1. **Record Efficiency for R2R-Fabricated PeSCs:** The researchers achieved a record-high power conversion efficiency (PCE) of 15.5% for individual small-area (0.08 cm²) roll-to-roll (R2R) printed perovskite solar cells. This represents a substantial improvement compared to previous fully R2R fabricated cells. 2. **First Demonstration of R2R-Fabricated Modules:** This work demonstrates, for the first time, the fabrication of perovskite solar cell modules entirely using industry-relevant R2R techniques under ambient room conditions. These modules, comprising serially interconnected cells, achieved a PCE of 11.0%. The active area of these modules was approximately 50 cm². 3. **Successful Replacement of Vacuum Deposition:** The use of printed carbon electrodes successfully replaced the expensive and less scalable vacuum-deposited gold electrodes, demonstrating that high efficiency can be achieved without vacuum processing. 4. **High-Throughput Optimization:** The high-throughput experimental platform enabled the rapid optimization of the fabrication parameters, leading to significant improvements in the cell performance. The researchers were able to test 1600 cells with 20 different parameter combinations within a short time frame. 5. **Cost-Effective Prediction:** A cost model predicted a production cost of -0.7 USD W−1 for a production rate of 1,000,000 m² per year in Australia. This suggests the potential for highly cost-competitive perovskite solar cells using this technology, with further cost reduction potential. Cost models also indicated that eliminating the remaining high-cost components (commercial TCEs and silver grids) could reduce the cost below 0.5 USD W−1.

This study makes a significant contribution to the field of perovskite solar cells by successfully demonstrating the fabrication of high-efficiency devices and modules using entirely roll-to-roll processing under ambient conditions. The use of printed carbon electrodes instead of vacuum-deposited gold electrodes, combined with the improved printing-friendly sequential deposition technique and the shallow-angle blowing technique, allows for a more cost-effective and scalable manufacturing process. The high-throughput experimentation platform played a critical role in rapidly optimizing the fabrication parameters, leading to the record-high efficiencies achieved in this work. The results of this study show the potential for roll-to-roll processed perovskite solar cells to become a cost-competitive alternative to traditional silicon-based solar cells, opening up new possibilities for large-scale deployment of this promising technology. While the efficiencies achieved in this work are still lower than the best laboratory-scale devices, the significant cost reductions projected make the technology attractive for large-scale production and application in various sectors such as building-integrated photovoltaics, flexible electronics, and portable applications.

This research successfully demonstrated the first entirely roll-to-roll fabricated perovskite solar cell modules under ambient room conditions, achieving a notable 11% efficiency for 50 cm² modules and 15.5% for individual small-area cells. The key innovations were the use of printed carbon electrodes, the optimization of perovskite crystallization using the shallow-angle blowing technique, and a high-throughput manufacturing and testing platform. The projected cost reduction to potentially below 0.5 USD W−1 (under optimistic scenarios) makes this technology promising for mass production and penetration into various markets. Future work could focus on further improving the efficiency of the modules by optimizing the interconnection techniques and developing even more conductive carbon-based inks to eliminate the need for printed silver grids.

The current R2R-fabricated modules have a lower geometric fill factor (GFF) than laser-scribed modules due to the limitations of the stripe-pattern approach used for cell interconnection. The screen-printed silver grid, while functional, may not be suitable for long-term outdoor operation due to potential corrosion issues. The current cost model projections rely on specific production rates and material costs, which might fluctuate in real-world scenarios. The study primarily focuses on the manufacturing process and cost aspects, and a more detailed long-term stability analysis under diverse environmental conditions could be beneficial to further assess the practicality of this technology for widespread use.