Pioneering Perovskite Scalability: Advancing Roll-to-Roll Slot Die Coating for Stable and Efficient Flexible Solar Cells

The rapid advancement of perovskite solar cells (PSCs) over the past decade has positioned
them as one of the most promising photovoltaic technologies in the future.1-2 Their unique
properties, including high power conversion efficiencies (PCE), tunable optical properties and

low-temperature processability, have opened up new avenues for lightweight, flexible and cost-
effective solutions for solar energy capture.

3 Achieving this requires a scalable manufacturing
process that ensures device efficiency, operational stability, and environmental sustainability.4
At TNO Solliance, we are developing roll-to-roll compatible processes, such as slot die coating
using green solvents and ambient processing conditions, to enable low-cost, high-throughput
manufacturing.
To address the associated challenges with scalability, we conducted roll-to-roll (R2R) coating
experiments on 30 cm wide flexible substrates at a web speed of 3 m/min, focusing on

optimizing drying conditions to enhance efficiency. We developed both opaque and semi-
transparent flexible p-i-n perovskite devices, achieving power conversion efficiencies (PCEs)

of up to 13% using roll-to-roll (R2R) compatible fabrication methods on polymer based
substrates. Thermal stress test (85 °C) confirmed initial stability after 1000 hours of continuous
exposure. Additionally, we have explored different hole transport layers (HTL) tailored for R2R
processing using non-toxic solvents and also investigated how variations in parameters impact
performance, stability and reproducibility.
Our approaches are also utilized in flexible metal foils, which offer several advantages, such as
mechanical flexibility, lightweight design, cost-effectiveness, and durability. Devices processed
via sheet-to-sheet (S2S) level on 15 × 15 cm2 flexible metal substrates achieved efficiencies of
up to ~15% with reproducibility. Preliminary results from these substrates processed using R2R
method further confirm their strong scalability potential. Additionally, S2S processed metal
foils using R2R compatible solvents deposited under ambient conditions showed efficiencies
exceeding 15% alongside excellent stability. Long-term stability tests on these substrates, where
non-encapsulated foils exhibited thermal stability for over 3000 hours at 85°C and 100°C.
Encapsulated devices withstand damp heat test(85°C/85% RH) and light-soaking test with
additional applied heat (55°C), maintaining both visual and performance stability for over 3000
hours, demonstrating robust, non-degrading perovskite architecture.
To further enhance the scalability and product adaptability our approach supports mass
customization through modular solar cell semi-fabricates. Using a combination of R2R
techniques and automated pick and place systems, individual cells can be tailored and

assembled flexibily either at the production site or final installation point. This enables on-
demand design for various applications from infrastructure integration to consumer electronics.

Our recent R2R development work has demonstrated promising stability and performance
metrics in various configurations. By systematically tuning the coating parameters and
exploring a range of stack designs, we have optimized uniformity and device reproducibility,
enabling the large-scale, commercially viable production of perovskite solar cells.