Bifacia™ is a transparent, space-grade CPI (colorless polyimide) substrate built for flexible solar arrays. Unlike opaque Kapton-type backings, its high optical transmission lets bifacial cells capture albedo - Earth-reflected light - on the rear face, turning the substrate into part of the power-generation system rather than inactive mass.

Two numbers matter, and they measure different things.

Peak gain: up to approximately 23% more instantaneous power when rear-face albedo is available under favorable orbit and attitude conditions.

Energy gain: approximately 13% more modeled accumulated energy per orbit in watt-hours, because albedo is not available for the full orbit.

Beyond rear-face power gain, approximately 90% transmission reduces absorbed heat and can keep the array roughly 10°C cooler, supporting cell efficiency and lifetime. The substrate's coefficient of thermal expansion is also matched to solar cells and interconnects, supporting dimensional stability through thermal cycling.

Bifacia™ is offered as the substrate platform. Other stack components and final system qualification remain customer or integrator defined.

Testing method: Atomic Oxygen exposure testing measures mass loss and erosion yield against a Kapton reference baseline.

Result: Bifacia™ CPI erodes at roughly half the rate of Kapton. Because the substrate is physically thicker - approximately 200 µm class - the time to full erosion is substantially longer.

What it means: on LEO missions where Atomic Oxygen is the dominant surface threat, the substrate carries meaningful margin. Rear and anti-ram faces receive additional protection from a dedicated coating tuned to orbit altitude; Atomic Oxygen flux at 300 km and 500 km differs by orders of magnitude.

The physics: the rear face operates on albedo light at approximately 400–1200 nm, outside the most damaging vacuum-UV band at 200–400 nm, reducing worst-case VUV exposure on that face.

Testing method: accelerated UV aging under a mercury-lamp source, tracking optical transmission and yellowing index.

Result: the current RX-127 grade retained transmission from approximately 88% to approximately 85.7% after roughly 2,850 equivalent sun hours, with minor yellowing. Stable optical performance matters because transmission loss directly reduces rear-face power.

Testing method: thermal-vacuum cycling across representative orbital hot and cold extremes.

Design basis: the substrate's coefficient of thermal expansion is matched to cells and copper interconnects, minimizing mechanical stress and warping through each day-night cycle.

What it means: the material is designed to reduce delamination and deformation risk through repeated expansion and contraction. Final shape retention and electrical integrity must be verified at completed-stack and mission level.

Approximately 90% of incident light is transmitted rather than absorbed. Cell arrangements also typically leave gaps of approximately 15% between cells. Together, these factors reduce total heat load and can lower operating temperature by roughly 10°C.

Lower temperature supports higher cell efficiency and slower long-term degradation. The thermal effect is evaluated as part of the thermal-vacuum test program.

The physics: high-energy protons pass through the cell and membrane; stopping them is not the role of a thin polymer substrate. Bifacia™ is designed to trap the larger population of low-energy protons that deposit energy inside the approximately 200 µm membrane, while high-energy protons transit the completed stack.

Testing method: proton irradiation at representative LEO energies, with optical transmission monitored before and after exposure to check for radiation-induced darkening.

Result: testing indicated low-energy proton capture without significant optical degradation. The substrate's radiation role is low-energy proton absorption combined with Atomic Oxygen and mechanical durability; high-energy proton hardness is addressed elsewhere in the system architecture.

Heliofold US ships concept samples to qualified prospects in small, easy-to-ship formats. Once specifications are agreed, typical lead time is around two months.

To begin, submit your mission profile - including orbit and altitude - along with array size and target timeline. The team will confirm sample format and next steps.

Open the Bifacia™ sample request form