News | Photovoltaic solar power
A wind of change is blowing through the space sector. Satellite constellations and low-cost missions are shaking up the traditional approach to space with a new appetite for high-volume components manufactured for the terrestrial market. This trend is driving innovation in low-cost space solar arrays while addressing key space requirements: sufficient power at end-of-life, high power density (W/g, W/m², W/m3).
Historically, silicon solar cells were developed for spatial applications. Then, in the 1990s, GaAs/Ge triple junction cells, then GaInP/GaAs/Ge, replaced silicon because of their high efficiency and their high resistance to irradiation (electrons and protons) . Today, III-V cells used for space combine several absorbers, to convert a large part of the AM0 solar spectrum , reaching record efficiencies up to 39.2% AM1.5g, for a thickness of about 150μm, which makes them relatively massive .
Currently, lead-based metal halide perovskites (ABX3) are positioning themselves as a breakthrough technology in the photovoltaic landscape . These materials are attracting a considerable amount of research and their photovoltaic conversion efficiencies have rapidly reached records of over 25% in single-junction configurations . In addition to these rapid advances in performance, the thickness of these cells are very thin (< 0.5μm of photoactive material) allowing very high power densities of about 30 W/g , which are 10 times higher than single-junction flexible thin-film silicon or GaAs cells. In addition, recent studies have shown the excellent resilience of this type of photovoltaic material to certain charged particle flows representative of the space environment [7,8].
Beyond accelerated aging tests in conditions representative of space, little data exists for this emerging technology on its performance in space environment, thus under multiple constraints (irradiation, UV, vacuum, thermal, etc.). It is therefore essential for the scientific community and industrial actors to study the behavior of perovskite devices in real flight conditions.
In partnership with Airbus Defense and Space and ONERA, the CEA had the opportunity to send perovskite mini-modules on a nano-satellite to study the evolution of their photovoltaic performances in space environment. The assembly is done on a 3U nano-satellite (10x10x30cm3) from the company Qosmosys (Singapore), whose cruising altitude is planned at 530km for a minimum operating time of 1 year. This altitude corresponds to a low earth orbit (LEO) in which the temperature amplitude between the eclipse and sun exposure phases will be [-50 ; +60°C].
This experiment should allow to follow two photovoltaic parameters: the open circuit voltage Voc on a device, and the short circuit current Isc on a second device.
The challenges are multiple: in the design of the architecture of the mini-modules and its integration with the electronic circuit board (PCB), taking into account the constraints of mass and geometry; in the materials used, qualified or compatible with the space environment; in the interconnection, which must be robust and reliable, without significant resistive losses; and in the very short time needed to provide the final prototypes
The CEA at INES has realized single junction perovskite mini-modules, made of 3 sub-cells shaped by laser steps, and assembled on a PCB. Initial measurements have shown good performances for these perovskite mini-modules, with a Voc of 3.36V and a Jsc of 27.4mA/cm² (AM0 spatial solar flux). These two parameters will be monitored in space after launch.
The launch of the nano-satellite took place successfully in January 2023; it is a first for a CEA photovoltaic technology and also a first flight test for this technology at European level. The telemetry data will allow us to study the evolution of the performance of the perovskite mini-modules in flight and to compare them with the monitoring of similar samples kept in our laboratories in order to de-correlate the intrinsic temporal instability of these perovskites from the environmental effects.
Eventually it may be decided to make a ground/flight correlation with prototypes of the same series, aged under similar conditions in an enclosure.
Our teams are impatient to analyze the data that are starting to arrive with the initialization of the nano-satellite.
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.