CZTS Solar Cells Hit 12.4% Efficiency: What It Means for India's Clean Energy Future

Researchers at the University of New South Wales (UNSW) in Sydney have achieved a record 12.4% power conversion efficiency for copper zinc tin sulphide — commonly known as CZTS — solar cells, alongside a record open-circuit voltage for the technology, marking a significant leap forward for thin-film photovoltaics that rely entirely on earth-abundant materials. The breakthrough, published in 2025, was made possible by controlling copper drift during the manufacturing process, a defect mechanism that has long suppressed voltage output and overall cell performance in CZTS devices. For India's solar energy ambitions — anchored to a 500 GW renewable energy target by 2030 under the National Solar Mission and the PM Surya Ghar Muft Bijli Yojana — this matters considerably. India currently imports the vast majority of its solar modules, overwhelmingly silicon-based cells predominantly sourced from China. A commercially viable CZTS alternative, built without rare or toxic elements like indium or cadmium, could fundamentally alter the economics and strategic calculus of domestic solar manufacturing under the government's Production-Linked Incentive scheme for solar PV modules.

What Makes CZTS Solar Cells Different From Conventional Silicon Panels?

CZTS solar cells belong to the thin-film photovoltaic family, which also includes cadmium telluride (CdTe) and copper indium gallium selenide (CIGS) technologies. The critical differentiator for CZTS is its material composition: it uses copper, zinc, tin, and sulphur — all elements that are abundant, inexpensive, and geopolitically accessible — instead of rare or hazardous metals. CIGS, for instance, depends on indium, a by-product of zinc smelting with constrained global supply, while CdTe relies on cadmium, a toxic heavy metal requiring careful disposal. For a country like India, which is aggressively scaling solar capacity through developers such as Adani Green Energy, ReNew Power, Greenko, and NTPC Renewable Energy, raw material security is a strategic priority. India's Ministry of New and Renewable Energy (MNRE) has explicitly flagged supply-chain resilience as a core concern in its solar manufacturing roadmap, and CZTS technology's reliance on non-critical minerals directly addresses that vulnerability. The UNSW team's specific advance was identifying and mitigating copper ion migration — a process during high-temperature fabrication steps that creates deep-level defects in the absorber layer, robbing the cell of voltage. By improving copper-sulphur bonding chemistry, the researchers suppressed this drift, enabling the record 12.4% efficiency figure.

To contextualise the significance: commercial silicon solar panels routinely achieve efficiencies between 20% and 23%, and premium heterojunction modules push beyond that. At 12.4%, CZTS is not yet competitive for utility-scale solar parks in Rajasthan or Gujarat. But the technology's trajectory is what the industry is watching. CIGS cells followed a similar arc — years of lab-scale incremental progress before reaching commercial thresholds above 20%. Every percentage point gained in CZTS efficiency narrows the commercialisation gap and strengthens the case for R&D investment by Indian institutes such as IIT Bombay, IIT Madras, and the National Institute of Solar Energy (NISE) in Gurugram.

How Does Copper Drift Suppression Unlock Higher Solar Cell Voltage?

The UNSW team's methodology centres on a well-known but historically difficult-to-control phenomenon in CZTS fabrication. During the high-temperature sulphurisation or annealing steps that convert precursor layers into the absorber film, copper ions — which are small and highly mobile — tend to migrate through the crystal lattice. This migration leaves behind copper vacancies and generates compensating defects that act as recombination centres, where photo-generated electrons and holes annihilate each other before they can contribute to electrical current. The result is a depressed open-circuit voltage, which is the primary efficiency bottleneck for CZTS relative to its theoretical maximum — a Shockley-Queisser limit estimated around 32% for this bandgap. By engineering stronger copper-sulphur bonds through modified precursor chemistry and controlled annealing atmospheres, the UNSW researchers reduced the density of these killer defects, pushing the open-circuit voltage to a record level for the material system. This is precisely the kind of materials-science advance that translation-focused institutions in India's renewable energy ecosystem need to monitor closely, particularly as MNRE and the Department of Science and Technology co-fund next-generation PV research under the National Mission for Strategic Knowledge for Climate Change.

The record voltage is arguably as important as the efficiency number itself. Open-circuit voltage deficit — the gap between a cell's theoretical and measured voltage — has been the defining challenge for CZTS since the technology emerged in the 1990s. Closing that deficit signals that the material's intrinsic recombination losses are being addressed at a fundamental level, not merely papered over with optical or contact engineering. That is a qualitatively different kind of progress, and it gives materials scientists a cleaner pathway to stack further improvements in current collection and light absorption on top of a stronger voltage foundation.

What This Means for India's Energy Transition

India's path to 500 GW of installed renewable energy capacity by 2030 — of which roughly 280 GW is expected to come from solar — demands not just deployment scale but manufacturing depth. The government's PLI scheme for solar PV modules, with an outlay of approximately ₹24,000 crore, is designed to catalyse domestic cell and module production. But PLI-supported factories are almost entirely oriented towards crystalline silicon today. CZTS, if it matures commercially, represents a potential second wave of thin-film manufacturing investment that could leverage India's existing metals and chemicals processing base. State-level solar parks in Rajasthan — home to the Bhadla Solar Park, the world's largest at 2,245 MW — Gujarat, Tamil Nadu, Andhra Pradesh, and Karnataka provide the deployment backbone, but the strategic prize is manufacturing sovereignty. A domestically produced thin-film technology built on abundant Indian minerals would reduce the import dependency that currently sees India spending billions of dollars annually on Chinese silicon modules.

Watch for MNRE and DST to increase collaborative funding calls with Australian institutions following this UNSW result — India-Australia clean energy research ties have been strengthening since the 2020 India-Australia Climate and Clean Energy Partnership. Domestically, NISE and IIT-based research groups are the ones best positioned to translate CZTS process insights into Indian manufacturing contexts. If efficiency crosses 14–15% within the next two to three years, expect the first serious conversations about pilot-line investment from Indian developers and the Solar Energy Corporation of India.