Researchers Created Indium-Free Tandem Solar Modules
A new tin-based electrode design maintains 31 percent efficiency while bypassing rare metal supply constraints.
Updated on Sept. 24, 2026 in Energy
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Researchers have developed high-efficiency tandem solar modules using tin oxide electrodes rather than indium. This research-stage development achieves a certified 31.0 percent efficiency for 32-square-inch minimodules.
Why it matters
The shift away from indium addresses critical supply chain vulnerabilities because indium availability is tied to zinc refining rather than direct mining. This work offers a path to cheaper, more stable materials as the solar industry continues to face silver supply deficits.
The indium-free minimodules achieved 31.0 percent efficiency, trailing slightly behind the 33.6 percent mark set by indium-based electrodes. These devices utilize tin oxide, a material costing roughly one percent of the price of indium.
The details
To create the modules, researchers utilized reactive plasma deposition—a process that uses an ionized gas to deposit thin, dense films onto surfaces—to apply tin oxide to delicate perovskite layers. This method prevents the degradation caused by conventional sputtering, a process that uses high-energy particles that damage the fragile interfaces within the perovskite cell. Perovskite is a versatile class of light-harvesting crystals that can be tuned to absorb different parts of the solar spectrum.
Timeline
The indium-free minimodules demonstrated 65 percent efficiency retention over 105 days of outdoor testing.
The global silver market has faced a supply deficit for the past 6 years.
Photovoltaic silver demand is projected to decline 19 percent in the current year.
The Tech Race
This development marks a shift toward material independence in the crowded race to scale tandem perovskite solar cells. By moving to tin oxide, researchers are attempting to circumvent the rare-metal constraints currently limiting the industry's material-cost reduction efforts.
This technology is currently in the research stage and not yet available for commercial purchase or consumer installation. The eventual adoption of these materials could lower solar module manufacturing costs by reducing reliance on expensive rare metals like indium.
The takeaway
This breakthrough proves that tin-based alternatives can reach efficiencies comparable to indium-heavy benchmarks. Interested observers should monitor future long-term stress tests to see if these modules can eventually match the 25-year lifespan required for standard commercial solar arrays.
Further reading
For more on the current transition toward new photovoltaic materials, visit /science/energy/.
Source note: This article includes information reported by Ecoportal.
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