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AM1.5G [168] ). Although GaAs multi-junctions still maintain extremely high efficiencies of ~34% under the
AM0 space spectrum [168] , the performance gap can narrow - or even reverse - after radiation exposure and
thermal cycling, as GaAs cells are expected to degrade by nearly 25% over several years in orbit [169] . Beyond
single-junction devices, tandem PSCs have shown remarkable progress, with efficiencies of 29.1% for
two-terminal perovskite-perovskite [106] and 34.85% for perovskite-silicon tandem devices . The latter is
[14]
comparable to III-V solar cells, while offering the potential for much higher specific power due to the
lightweight nature of perovskites. However, scaling PSCs from laboratory-scale devices to large-area modules
(> 100 cm ) without significant efficiency loss remains a challenge [170] . Recently, perovskite panels with an
2
aperture area of 0.73 m and 12.0% efficiency were demonstrated by interconnecting 156 cm modules with
2
2
individual efficiencies of 16.3% [Figure 5D and E] [171] . These advances highlight the rapid progress toward
large-area PSCs, although they still lag behind III-V multijunction panels with proven meter-scale
fabrication [172] . Continued improvements in perovskite efficiency, combined with their inherent radiation
tolerance, could substantially reduce the cost of space-grade solar power.

Cost and manufacturing
One of the most compelling advantages of PSCs for space applications is their potential for dramatic cost
reduction. Conventional space-grade III-V multi-junction solar cells remain extremely expensive - typically
several hundred to over one thousand USD W - due to epitaxial growth on costly substrates and limited
1
mass production [173] . c-Si modules are cheaper at terrestrial module levels (0.2-0.4 USD W ), but
-1
radiation-hardened silicon architectures adapted for space also incur elevated costs because of specialized
processing [174] . PSCs, in principle, can be fabricated using scalable solution-based or roll-to-roll
techniques [175] , with preliminary estimates suggesting module manufacturing costs below 0.1 USD W once
-1
stabilized high-efficiency modules are realized [176-178] . More recent technoeconomic modeling studies indicate
that, under favorable stability and scale-up scenarios, the levelized cost of electricity (LCOE) for PSCs could
fall in the range of 0.04-0.25 USD kWh , making them competitive with c-Si and III-V PVs in applications
-1
such as satellite mega-constellations, where deploying large quantities of solar panels renders traditional PV
economically unfeasible [179] . Lower PV costs could also expand mission design options, enabling concepts
such as expendable solar arrays or increased on-board power availability for electric propulsion systems .
[180]
However, these projections remain theoretical in the space context. The transition from laboratory-scale
devices to qualified space-grade modules will require extensive testing for encapsulation, radiation
hardening, and long-duration operation. Initial deployments are therefore likely to be expensive, mirroring
the early trajectory of other PV technologies. Nonetheless, the ability to leverage terrestrial thin-film
manufacturing infrastructure, combined with the intrinsic advantages of PSCs in mass per watt, presents a
credible pathway toward cost breakthroughs in space photovoltaics.

Challenges and considerations
Sections "Adapting to the AM0 space solar spectrum"-“Radiation-induced performance enhancements” have
highlighted the performance characteristics of PSCs relevant to space applications. As summarized in
Table 1, PSCs demonstrate competitive efficiency, specific power, and radiation tolerance compared with
GaAs- and Si-based photovoltaics, while remaining at an earlier stage of technological maturity. Despite
these attractive properties, PSCs face several challenges before they can be adopted as mainstream space
technologies. The foremost challenge is long-term operational stability. Although radiation-induced
degradation in PSCs is often less pronounced than in conventional solar cells, the combined influences of
multiple space stressors - including high vacuum, ultraviolet irradiation, and repeated thermal cycling - over
multi-year missions remain insufficiently characterized. Robust encapsulation will be essential, as even
minor breaches can accelerate degradation pathways, for example, through residual outgassing or
UV-induced chemical reactions . By contrast, GaAs solar cells have demonstrated decades of in-orbit flight
[181]
heritage with well-understood failure modes, which underpins space agencies’ confidence in their use [182,183] .