With the development of emerging fields such as wearable electronics and integrated building photovoltaics, flexible perovskite solar cells show tremendous application potential due to their bendability, lightweight, and windable properties. However, the key to industrialization—roll-to-roll coating technology—is facing severe tests from three major technical bottlenecks.

1. Dynamic Deformation and Tension Control of Flexible Substrates

Traditional rigid substrate coating processes are undergoing fundamental changes in flexible scenarios. Flexible substrates such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) exhibit elastic deformation at high speeds of 50 m/min, as well as plastic deformation, causing continuous changes in the actual geometric parameters of the coating area.

Solution:

- Multi-stage tension zone control is used to precisely regulate tension in the unwinding, coating, drying, and winding areas

- Introduction of a laser ranging system to monitor substrate deformation in real time and adjust roller speed through closed-loop feedback

- Optimized guide roller layout design to reduce wrapping angles and minimize substrate stress

2. Thermal Management Challenges in High-Speed Continuous Production

In roll-to-roll continuous production, the crystallization process of perovskite films needs to be completed within a limited drying area. Under high-speed operating conditions, traditional drying methods such as hot air drying and near-infrared radiation easily cause solvent evaporation too quickly, resulting in pinhole defects. At the same time, the temperature resistance limit of flexible substrates (usually ≤ 150°C) further constrained the process window.

Innovation Path:

- Developed a gradient temperature field drying system to achieve stepwise evaporation of solvents

- Uses pulsed intense light annealing technology to complete perovskite crystallization in milliseconds

- Introduction of air-floating drying devices to prevent thermal loss caused by contact between the substrate and the rollers

3. Dynamic process precision control technology

To achieve <5% film thickness uniformity, three major dynamic accuracy challenges must be overcome: micron-level stability between the coating head and substrate gap, precise synchronization of coating speed and substrate speed, and real-time consistency of precursor ink viscosity.

Technical Breakthroughs:

- Developed a laser inspection system that provides real-time feedback and adjustment of coating parameters

- Uses dual servo motor synchronous drive technology to ensure a speed matching accuracy of 99.5% between the coating unit and traction unit

- Equipped with online testing of film crystallization quality, combined with a temperature control system to maintain stable solution rheological characteristics

Technical outlook

Currently, industry-leading companies have achieved stable 24-hour continuous production on a 300mm wide flexible substrate through system integration of the above technologies, with film thickness uniformity controlled at ±4.8% and line speeds reaching 35m/min. Next, the R&D focus will focus on:

- Develop adaptive algorithms to achieve intelligent adjustment of process parameters

- Innovative passivation technology to enhance the durability of flexible devices under bending conditions

- Optimized coating head flow channel design to accommodate higher solid content perovskite inks

Only by breaking through these key technical bottlenecks can flexible perovskite solar cells truly move from the laboratory to industrialization, opening up broader application space for next-generation photovoltaic technologies.