What UNSW's Xiaojing Hao Just Got Right About Earth-Made Solar for Space

Who Is Xiaojing Hao, and Why Does Her Lab Matter Right Now?

Professor Xiaojing Hao leads the photovoltaics research group at the University of New South Wales (UNSW) in Sydney, one of the few teams in the world doing serious materials science on copper-zinc-tin-sulfide (CZTS) solar cells — a thin-film technology built entirely from Earth-abundant, non-toxic elements. Her group's recent achievement is the kind of quiet, rigorous result that tends to outlast the press releases surrounding it: the UNSW team has reached a 12.4% power-conversion efficiency and a record open-circuit voltage for CZTS solar cells by preventing copper drift during manufacturing, a defect mechanism that has plagued this material class for over a decade.

What Does 12.4% Efficiency Actually Prove — and What Doesn't It Prove Yet?

To place this milestone on the demo-to-deployment curve: 12.4% efficiency, achieved in a university laboratory setting as of 2026, is not yet competitive with the 22–24% figures routinely cited for commercial CIGS (copper indium gallium selenide) thin-film panels, nor the 29–30% range achievable with III-V multijunction cells preferred for satellite power systems. What it does prove is that the copper-drift problem — the tendency of copper atoms to migrate through the absorber layer during high-temperature processing, creating recombination defects that cap voltage — is a solvable engineering problem, not a fundamental materials limit.

CZTS, explained for colleagues new to the material: Copper-zinc-tin-sulfide (CZTS) is a thin-film photovoltaic absorber made from four elements that are cheap, abundant, and free of the indium and gallium supply-chain constraints that shadow CIGS. The core challenge is that copper and zinc atoms are nearly identical in size, so they swap lattice sites readily, creating "antisite" defects that reduce the voltage a cell can deliver. Professor Hao's team addressed this by improving copper-sulphur bonding chemistry during deposition, reducing those defects at the source rather than trying to anneal them out afterward — a process-level fix with real manufacturability implications.

The UNSW result (PV Tech, 2026) also sets a record open-circuit voltage for the material class, which matters more than the headline efficiency number. Voltage is the parameter most sensitive to defect density; a record Voc at this efficiency level means the team has genuine headroom to push efficiency further without a materials breakthrough — just continued process refinement.

Why Should Space Solar Planners Care This Week?

The relevance to space-based solar power (SBSP) and spacecraft power systems is strategic, not immediate. Today's satellite and SBSP designs specify III-V multijunction cells because their specific power (watts per kilogram, W/kg) is unmatched at orbital illumination conditions. CZTS at 12.4% does not challenge that hierarchy today.

But the field has a supply-chain and cost problem that CZTS directly addresses. Every serious SBSP architecture — from the European Space Agency (ESA) SOLARIS concept to the US Naval Research Laboratory's power-beaming demonstrators — faces the same long-pole challenge: deploying gigawatts of photovoltaic area in orbit at a cost per watt that can be justified against terrestrial solar-plus-storage, which currently sits well below 50 USD per megawatt-hour in sun-rich regions. That cost equation depends partly on launch cost per kilogram (falling, but still above 1,000 USD/kg on most vehicles), and partly on cell manufacturing cost. An Earth-abundant thin-film technology with no indium, no gallium, and no toxic cadmium in the absorber layer is a fundamentally lower-cost manufacturing story — if efficiency can reach the high teens.

The Actionable Takeaway for Your Roadmap

If you are evaluating photovoltaic supply chains for a future SBSP program or a lunar surface power system, add CZTS to your technology watch list at Technology Readiness Level (TRL) 4 today — proven in a relevant laboratory environment — with a credible path to TRL 6 (prototype demonstration in relevant environment) within this decade if the UNSW group's process fix scales to larger substrates. The record voltage result from Professor Hao's team is the signal that the material's ceiling is higher than prior efficiency plateaus suggested.

The practical decision for program managers: engage with UNSW now, before this result attracts the consolidation interest it deserves. A university group that has just solved a decade-old defect problem is precisely the partnership moment that gets missed when teams wait for a commercial spinout to form. Professor Hao's lab has done the hard work. The next step is yours.