Researchers have developed a new type of solar cell that demonstrates significant resilience to the harsh radiation found in space. The study indicates that cadmium telluride-based photovoltaics could provide more reliable, long-term power for the growing number of satellites in Earth's orbit, potentially outperforming some current technologies.
As the demand for near-Earth satellites increases, so does the need for durable power systems. A recent investigation into cadmium selenide telluride (CdSeTe) solar cells shows they maintain their efficiency remarkably well after exposure to proton radiation, a key factor in the degradation of space-based electronics.
Key Takeaways
- New cadmium selenide telluride (CdSeTe) solar cells have shown strong resistance to proton radiation.
- In simulated tests, the new cells retained a higher percentage of their initial efficiency compared to some standard space-grade solar cells.
- This improved durability could allow for longer satellite missions and more reliable power systems in high-radiation environments.
- The findings suggest that cadmium telluride, a previously underutilized material for space, holds significant potential for future applications.
The Challenge of Powering Satellites in Space
The space environment presents a major challenge for any long-term mission. Satellites orbiting the Earth are constantly bombarded by charged particles, primarily protons, which can damage their electronic components, including their power source.
Currently, most satellites rely on multijunction III-V photovoltaics (PVs), a type of solar cell known for its high efficiency. However, these cells degrade over time due to continuous radiation exposure. This degradation limits the operational lifespan of a satellite and must be factored into its design.
Understanding Space Radiation
Satellites, especially those in medium-Earth orbit (MEO), pass through regions of intense radiation like the Van Allen belts. This environment contains high-energy protons and electrons trapped by Earth's magnetic field. This constant exposure slowly breaks down the crystalline structure of solar cells, reducing their ability to convert sunlight into electricity.
The growing satellite market, driven by communications, Earth observation, and navigation services, requires power systems with greater energy capacity and enhanced reliability. A satellite's mission is often limited by the end-of-life performance of its solar panels.
A Promising New Material Emerges
A research team led by Zachary W. Zawisza investigated an alternative material: cadmium telluride (CdTe). While common in terrestrial solar panels, its potential for space has been largely overlooked. The study focused on a variation called cadmium selenide telluride (CdSeTe).
Scott Lambright, an author of the study, highlighted the material's untapped potential.
“The potential value of CdTe single-junction solar cells and their use as a partner in a tandem solar cell have been underappreciated,” Lambright said.
The researchers created and tested two versions of the CdSeTe cells, one doped with copper and the other with arsenic. Doping is a process where small amounts of other elements are added to a semiconductor to alter its electrical properties.
Performance Under Simulated Space Conditions
To measure their durability, the scientists exposed the new CdSeTe solar cells to proton radiation that simulated a three-year mission in a medium-Earth orbit environment. They then compared their performance to that of existing multijunction III-V PVs.
The key metric was the efficiency remaining factor, which measures how much of a solar cell's initial performance is left after being exposed to radiation. The results were significant.
Key Finding
The copper-doped CdSeTe solar cells outperformed two of the three standard multijunction III-V PVs used in the comparison. They maintained a higher photoconversion efficiency after the simulated three-year radiation exposure, indicating superior resilience.
This outcome suggests that satellites equipped with this new technology could operate for longer periods or maintain higher power levels throughout their missions. This is especially important for missions in high-radiation orbits or those with extended service life requirements.
“Considering that satellites are generally designed around the end-of-life performance of their power systems, this suggests that CdSeTe-based PV modules are the preferable technology for high-exposure or long service-life missions,” Lambright explained.
Future Research and Development
The promising results from this initial study have paved the way for further investigation. The research team plans to conduct more tests on the CdSeTe solar cells to ensure they meet the rigorous standards required for space qualification.
Future work will also focus on understanding the fundamental physics behind the cells' resilience. Scientists want to identify the specific types of defects caused by radiation and explore how they might be repaired.
Next Steps in the Investigation:
- Defect Analysis: Researchers will study the energy levels, densities, and stability of radiation-induced defects in the material.
- Healing Mechanisms: The team will investigate whether damage can be reversed using thermal annealing (heating) or light-based annealing (exposure to light).
- Standardized Testing: The cells will undergo a full suite of tests based on established protocols for space-grade photovoltaics.
According to Lambright, these studies aim to “understand the primary causes of reductions in efficiency and how the various defects may heal.” This deeper understanding could lead to even more robust and efficient solar cell designs for the next generation of space exploration and satellite technology.