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In-orbit tests and long-term stability
Beyond laboratory experiments in controlled environments, several studies have successfully tested the
durability of PSCs in real space environments [Figure 2D] . The stratosphere, the second-lowest layer of
[40]
Earth’s atmosphere (20-50 km altitude), can be reached by high-altitude balloons . Cardinaletti et al.
[40]
launched a balloon incorporating PSCs based on MAPbI to 32 km for over 3 h, where the temperature
3
varied from -53.2 to 16.9 °C . The devices retained 64% of initial PCE, showing degradation due to phase
[41]
transition from the cubic phase to the tetragonal phase at temperatures below 57 °C and increased interfacial
recombination at the electron-selecting contact.

In another experiment, PSCs based on MA 0.17 FA 0.83 Pb(I 0.17 Br 0.83 3
) (MA = methylammonium,
FA = formamidinium) were launched on a sub-orbital rocket with a parabolic trajectory reaching ~240 km
altitude, where they experienced microgravity and negligible atmospheric effects . During three different
[42]
illumination phases over 360 s of main measurement, the PSCs showed slight decrease in power density and
reduced hysteresis due to reduced charge carrier accumulation and interfacial recombination. This difference
was attributed to altered illumination conditions rather than radiation-induced damage.

Most impressively, perovskite films were subjected to continuous LEO conditions at an altitude of 408 km
for 10 months on the ISS in 2020-2021 [15] . The samples, fabricated with the structure of
borosilicate/encapsulant/SiO /MAPbI /borosilicate, exhibited partial degradation: borosilicate turned yellow
3
2
under electron radiation, while bubbles trapped in the encapsulant induced perovskite decomposition into
PbI . In addition, extreme thermal cycling (> 200 °C swings per orbit) induced strain in the perovskite lattice.
2
But intriguingly, upon re-illumination on Earth, the accumulated stress gradually relaxed under sunlight,
leading to effective recovery of the initial structure, reduced defects, and increased charge carrier lifetime.
Overall, these in-orbit demonstrations confirm that, with proper encapsulation, perovskites can remain
stable for extended durations in LEO, supporting their feasibility for multi-year satellite missions. The next
steps will be multi-year orbital tests of fully operational perovskite solar arrays.

LIGHTWEIGHT AND FLEXIBLE DESIGN CONSIDERATIONS FOR LEO APPLICATIONS
Ultra-high specific power and power-to-weight ratio
PSCs can be fabricated with an extremely thin active layer of a few hundred nanometers , and devices can
[43]
be built on ultralight substrates such as plastic films, thin metal foils, or 10-50 µm glass [44-47] . Consequently,
the power output per unit weight of PSC devices is higher than that of today’s space solar panels.
State-of-the-art flexible PSCs have demonstrated specific powers on the order of 20-30 W g -1[48-50] .
Kaltenbrunner et al. reported that a 300 nm thick PSC on a plastic foil achieved a specific power of 23 W g -1
using a lightweight encapsulant, with a Cr O /Cr interlayer enabling air-stable operation by protecting metal
3
2
contacts . Zhang et al. also reported polyethylene terephthalate (PET) substrate-based flexible PSCs using a
[48]
pyridine-promoted growth method to obtain high-quality perovskite films, achieving a PCE of 14.19% and a
specific power of 23.26 W g -1[51] . Thus, recent analyses indicate that fully optimized designs can achieve PSC
specific powers close to ~30 W g -1[52] , approaching the theoretical limits for any PV technology. This is over
an order of magnitude higher than the specific power of conventional space solar technologies based on rigid
silicon PV panels (0.5-2 W g ) and III-V multi-junction GaAs-based solar cells on lightweight substrates
-1 [53,54]
(~5.5 W g ) . Figure 3A shows the power-to-weight ratios of various PV technologies . The implications
[58]
-1 [55-57]
for space are significant, as reducing the mass of solar arrays increases payload capacity or reduces launch
costs. A perovskite PV array is lighter than a silicon PV array for the same power output. This high specific
power enables large-area or rollable solar panels that were previously infeasible with heavier, rigid
photovoltaics. In short, perovskite photovoltaics allows highly efficient power generation without the mass
penalty of traditional PV panels, making it highly attractive for both LEO satellite constellations and
deep-space probes.