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Page 6 of 22 Song et al. Energy Mater. 2026, 6, 600019

Figure 3. (A) Comparison of the power-to-weight ratios of various photovoltaics [58] Copyright © 2023, Springer Nature. (B) Photograph of
a researcher holding a roll of printed PSCs on a plastic substrate (CSIRO, Australia) . (C) PSC based on PET/Ag mesh/PH1000 and its
[71]
bending test, reported by Li et al. [76] Copyright © 2016, Springer Nature. (D) Scanning electron microscope (SEM) images of the top and
bottom surfaces of a control perovskite film and a bifacial 2D-capping-layered perovskite film after 10,000 convex and concave bending
cycles, reported by Jin et al. [80] Copyright © 2025, Springer Nature.

Flexible substrates and mechanical robustness
Another advantage of perovskites is that they can be fabricated on flexible substrates using low-temperature
processes. Unlike III-V multi-junction solar cells, which are grown on rigid wafers, PSCs can be fabricated at
temperatures below ~150 °C [48,59] , using polymer films, metal foils, or thin glass as substrates. Polyimide
(Kapton) substrates tolerate space temperatures up to ~400 °C and have excellent mechanical strength [60-62] , as
well as PET [63-65] /polyethylene naphthalate (PEN) films [66,67] for low-cost roll-to-roll manufacturing. Ultrathin
(< 1 mm) flexible glass is another attractive substrate, offering flexibility along with superior barrier
properties against moisture and oxygen ingress. Metal foils, such as titanium or aluminum, can serve as both
substrate and encapsulant, providing mechanical robustness and thermal management [68-70] . The integration
of flexible substrate-based solar cells indicates that the entire solar arrays can be designed for folding, rolling
and stowing compactly during launch and then deploying to large areas in orbit. This is ideal for small
satellites or deployable structures such as roll-out solar blankets. Figure 3B shows a flexible perovskite PV
module . Thus, the mechanical durability of PSCs under bending and vibration has recently attracted
[71]
attention and shown promising results. Typically, flexible PSCs maintain high performance under tight
bending radius and repeated flexing [72-75] . Li et al. reported that the PSCs on
PET/Ag-mesh/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, PH1000) substrates