Rocket Lab has released its IMM Apex solar cell with a beginning-of-life efficiency of 31.5%
The germanium-free cell has 40% lower mass and is designed to withstand radiation and temperature changes in space
It is mechanically and electrically compatible with conventional germanium-based space solar cells
US space technology company Rocket Lab has released its Inverted Metamorphic (IMM) Apex solar cell for space applications. The company says the cell offers 31.5% efficiency and 40% lower mass.
Beginning-of-life efficiency refers to the cell’s performance at the start of a space mission, before prolonged exposure to radiation and other conditions in space. According to Rocket Lab, the cell is designed to maintain its performance under radiation and changing temperatures.
The company also states that IMM Apex has 40% lower cell mass. Combined with its conversion efficiency, the reduced weight increases the cell’s specific power, which indicates the amount of power generated relative to its weight. This is important for spacecraft, as reducing the weight of one component can lower the overall spacecraft mass or free up capacity for other equipment.
A key feature of IMM Apex is that it eliminates the germanium substrate used in conventional multi-junction space solar cells. Germanium substrates have been widely used in this segment for around three decades. However, Rocket Lab says rising material costs and supply constraints are creating challenges for the space power industry.
In IMM solar cell production, the semiconductor layers are initially grown in reverse order before the structure is transferred, and the original growth substrate is removed. This approach lets researchers optimize the different light-absorbing layers while reducing substrate weight.
Despite its germanium-free structure, IMM Apex is designed as a mechanical and electrical drop-in replacement for existing germanium-based solar cells. This means spacecraft manufacturers can integrate it into existing designs without making major changes to their systems or manufacturing processes.
Rocket Lab said it has optimized the manufacturing process and made targeted investments to support production in the multi-100 kW range. The company expects this capacity to help meet growing demand for space-based solar power. IMM Apex is now commercially available.
IMM Apex is the latest version of Rocket Lab’s IMM solar cell technology, which has undergone more than a decade of testing and qualification. Earlier IMM cells powered NASA’s Ingenuity Mars Helicopter and have also powered satellites in orbit for more than 10 years.
“IMM Apex delivers exceptional performance while addressing real-world challenges like rising material costs and supply chain constraints,” said Brad Clevenger, President of Rocket Lab USA. He added that the product combines high efficiency, low weight, and faster production without compromising performance.
Rocket Lab supplies space-grade solar products for civil, national security, and commercial space programs. Its technology has been used in programs including the James Webb Space Telescope and NASA’s Artemis lunar missions. According to the company, more than 1,100 satellites currently in orbit are powered by its solar products.
