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Song et al. Energy Mater. 2026, 6, 600019 Page 7 of 22

retained over 95.4% of their original efficiency after 5,000 bending cycles of 5 mm radius. Additionally, PSCs
endured with a few mm curvature (r = ∞, 7, 5, 3.5 and 2 mm), retaining 98.1% of the original PCE value
[Figure 3C] . One strategy to improve the flexibility of PSCs is to incorporate 2D/3D perovskite interfaces
[76]
or strain-relieving additive microstructures, which act as micro-shock absorbers in the film [77-79] . Accordingly,
introducing a bifacial 2D capping layer that cushions grain boundaries has recently been reported to achieve
~80% PCE retention after 10,000 bending cycles at a 3 mm radius [Figure 3D] . The thin device is capable
[80]
of being bent or rolled while continuing to generate power. The ability of PSCs to endure high vibration
during launch and flexural stress during deployment without cracking is a critical prerequisite for space solar
panels.

Space-grade encapsulation and thermal management
Operating in LEO exposes solar cells not only to radiation but also to vacuum, extreme temperatures, and
atomic oxygen. Notably, the exposure of perovskite photoactive layer to oxygen with light results in
superoxide (O ) species, enabling deprotonate the cation of photo-exited perovskite, leading to the
-
2
formation of PbI , water, methylamine and iodine . Furthermore, atomic oxygen can cause corrosion,
[81]
2
surface texturing, or the formation of metal oxides in the metal electrode contacts, all of which contribute to
the degradation of PSCs in LEO . Therefore, an effective encapsulating technology is vital to protect
[82]
perovskite devices and ensure long-term stability. Space PV encapsulation must have multiple roles,
including sealing the cell from vacuum and oxygen, maintaining transparency to radiation, withstanding
thermal cycling, and blocking UV and atomic oxygen [83-85] . Traditional space solar cells use rigid cover glasses
fused silica with anti-reflective coating for bonding over the cell, which results in significantly increased
mass. Although the traditional encapsulated glasses have high transparency, UV radiation absorption and
high durability, they are not suitable enough for space perovskite photovoltaics. From these reasons, more
innovative lightweight encapsulations are being developed for PSCs [82,86-88] . A common approach is to use
ultra-thin barrier films composed of multilayer inorganic/polymer coatings, often deposited by atomic layer
deposition (ALD). For example, an ALD-grown Al O layer of a few nanometers in thickness on a polymer
3
2
sheet can dramatically reduce moisture and oxygen permeation, with negligible added weight . Edge sealing
[89]
with low-outgassing epoxies or thermoplastics is used to prevent vacuum ultraviolet penetration and isolate
the cell’s edges [83,90] . Flexible glass or polyimide/fluoropolymer sheets can act as the outer layers, offering both
mechanical protection and atomic oxygen resistance [91-94] . The PV encapsulation must also minimize optical
loss. Therefore, the encapsulation materials are required to be transparent across the solar spectrum to avoid
attenuating the incoming sunlight.

A corresponding challenge for fully flexible perovskite photovoltaics is managing thermal stress. Perovskite
cells in orbit cycle through temperatures from roughly -150 °C (night side) to +150 °C (sun side). Such
thermal cycling can induce expansion mismatch between the different layers of the cell, causing mechanical
issues. To address this, researchers are incorporating stress-relief elements into the module stack. A practical
strategy is to match the coefficients of thermal expansion (CTE) of the substrate and transport layers with
that of the perovskite layer, thereby reducing differential strain [95-97] . Alternatively, introducing an elastic
buffer layer or adhesive within the encapsulation can absorb some of the expansion and contraction, such as
a silicon-based encapsulant that remains pliable at low temperatures . Careful optimization of material
[93]
selection and device engineering allows perovskite panels to tolerate repeated thermal cycling without
cracking or delamination. Notably, in ISS experiments, employing a specialized encapsulation architecture
comprising a thin glass superstrate and edge sealant enabled the devices to endure nearly one year of orbital
cycling without degradation .
[98]