Perovskite solar cells (PSCs) have attracted significant attention from both academia and industry, primarily due to their exceptional optoelectronic properties which enable high power conversion efficiencies (PCEs) of up to 26.7%¹. Additionally, their abundance of constituent elements and the potential for low-temperature, solution based thin-film processing make them attractive for cost-efficient, high-throughput production. Flexible PSCs, with their mechanical resilience and compatibility with roll-to-roll (R2R) fabrication, offer a promising pathway for large-scale applications. Despite advancements at lab scale, scaling PSC technology to industrial levels remains challenging. Key issues include adapting fabrication processes to industrial equipment while maintaining efficiency, achieving long-term operational stability comparable to commercial photovoltaic technologies with lifespans exceeding 20 years, and ensuring economic and environmental viability.

In this study, we address these obstacles by demonstrating the scalability of PSC technology through the use of R2R-compatible processing equipment. Our approach utilizes flexible aluminum foils with unique benefits such as high flexibility, lightweight properties, low cost, and excellent durability². Additionally, their high-temperature processing capability facilitates the use of advanced materials, including indium-free fluorinated tin oxide (FTO) electrodes and nickel oxide (NiO_x) hole transport layers (HTL), which are challenging to implement on conventional flexible substrates.

Perovskite solar cell stacks were deposited on various aluminum (Al) foil substrates using R2R-compatible methods and solvents. Prototype devices processed at the sheet-to-sheet (S2S) scale on 15 × 15 cm² Al/FTO substrates achieved efficiencies of up to ~15% with high reproducibility. Preliminary results of PSCs processed on Al/FTO substrates via the R2R method further underscore the strong scalability potential of this approach. Additionally, S2S-processed Al/ITO devices, fabricated using R2R-compatible solvents  under ambient conditions, showed efficiencies exceeding 15%, with outstanding stability.

Stability tests focused on PSC devices fabricated on Al/ITO substrates, where non-encapsulated devices exhibited thermal stability for over 3000 h at 85°C. To further assess device stability, damp heat test (85°C/85% RH) and light-soaking test, with additional applied heat (55°C), were conducted on encapsulated devices. The tested devices maintained visually stable for over 3000 h further supporting the robustness of these flexible perovskite solar cells.

Moving forward, we aim to enhance the efficiency, yield, stability and scalability of PSCs. Specifically, our focus will be to improve device efficiencies to levels comparable to lab-scale cells, approaching 20%. Additionally, we will work on achieving improved statistical distribution of efficiencies across larger areas, ensuring higher yield and reproducibility. Stability will be further evaluated through extended light-soaking tests under elevated temperatures, as well as rigorous indoor and outdoor performance testing. To advance scalability, we plan to transition from small-area prototypes to the fabrication of larger-area modules, paving the way for industrial-level production.

¹ https://www.nrel.gov/pv/interactive-cell-efficiency.html

² https://www.hyetsolar.com