Nano-C | From Grams to Tonnes: The Materials Behind Perovskite-Silicon Tandem Commercialization
In 2026, certified perovskite-silicon tandem cell efficiencies surpassed 35%, extending the performance lead of tandem architectures beyond the theoretical 29% limit of silicon photovoltaics. This confirms what the research community has argued for a decade: stacking a perovskite top cell on silicon is the most practical route to the next big step in solar efficiency. Translating these laboratory results into commercially manufactured modules, however, requires more than continued gains in peak efficiency.
In an industry that is bombarded by announcements about record breaking efficiencies and GW scale capacity plans, these are not realities that the industry operates under today. While Gigawatt-scale tandem lines are being built, they are running at a fraction of nameplate capacity or simply just running their pilot lines.
The first commercial full-size tandem modules at industrial scale are expected to launch between 2028 and 2030 with efficiencies between 26% to 30%. For the leading manufacturers, the question is no longer whether perovskite-silicon tandems work; it is whether they can be made by the millions, at high yield, with lifetimes and stabilities that make the economics work for bankable projects.
The answer largely depends on the few layers most people never see, some of them only a single molecule thick. The companies that can figure out which combination of materials and which process technologies achieve the best balance for stability and performance will have an advantage. This article looks at why those layers matter, what changes when their supply moves from the laboratory to the factory, and where the next round of performance gains is likely to come from.
It is these very layers where Nano-C is a key supplier to the solar industry. Founded in 2001 from pioneering MIT research, Nano-C has been pushing device performance to new heights through the innovative use of materials while also building a tier 1 industrial supply chain. Today, the company combines vertically integrated production with application expertise in solar, batteries and semiconductor materials. As perovskite technologies move towards large-scale manufacturing, Nano-C supports manufacturers with an expanding portfolio of ETL, HTL and transparent conductor materials engineered for industrial deployment.
Lab Efficiency Has Seen Incredible Success; Now It’s Time to Make It
A research lab and a factory measure success differently. A lab can fabricate twenty cells, report the best one and move on. A factory lives on the median of millions: every fraction of a percent of yield lost to a bad batch, a drifting process or a material that behaves differently from one delivery to the next comes straight off the bottom line. Reliability raises the bar further. Modules must pass damp-heat, thermal-cycling and light-soaking tests, and buyers and lenders expect performance warranties measured in decades.
This changes how materials are judged. Properties that barely register in a research setting, such as lot-to-lot variability, trace impurities and documentation, become sources of yield loss or reliability risk on a production line. There is also a timing effect that is easy to overlook. Once a material is qualified into a production process, replacing it usually means repeating reliability testing and requalifying the line, which innovation strategy can take many months. The materials chosen for today's pilot and first commercial lines are largely set, but now the leading companies are turning their gaze to multi-gigawatt-scale production. For tandem manufacturers, supplier selection is a long-term decision, and it is being made now.
Where Perovskite Solar Cells Win or Lose
Most perovskite-silicon tandems in development today use a p-i-n top cell (Figure 1). Light passes through a transparent electrode and an electron transport layer (ETL) before reaching the perovskite absorber, which sits on a hole transport layer (HTL) above the silicon bottom cell. The perovskite gets most of the attention, but the transport layers determine how efficiently charge gets out of it.
In leading devices, the ETL is typically thermally evaporated C60 fullerene, a layer around 20 nanometres thick, thousands of times thinner than a human hair. The HTL comprises increasingly a self-assembled monolayer (SAM): a single layer of molecules that anchors to the underlying electrode, a metal oxide or interconnection layer (ICL) and presents a tailored surface to the perovskite. These interfaces are where much of the remaining voltage loss in today's best cells occurs. The perovskite/C60 interface in particular is widely recognized as a major site of non-radiative recombination, and it can also be a mechanical weak point, where poor adhesion contributes to delamination under stress.
Because of this, the materials at these interfaces influence efficiency, yield and lifetime all at once. A small change in ETL purity or HTL coverage can shift open-circuit voltage, narrow a process window or change how a module ages in the field.
By the Numbers: From Grams to Tonnes
Thin does not mean small. At around 25% module efficiency, one gigawatt of tandem modules covers roughly four million square metres. A 20 nm C60 layer across that area adds up to about 130 kg of deposited fullerene into a solar cell, however, considerably more must be loaded into evaporators once material utilization is considered. A material that most researchers have historically bought by the gram is about to be needed by the tonne, every year, with every kilogram held to the same specification.
What Volume Readiness Looks Like
As tandem manufacturers move from pilot to volume production, they are asking materials suppliers the same questions they ask their equipment vendors. Can you deliver at scale? Is every batch the same? Can you trace a problem back to its source? And can you keep up as we grow? Answering those questions is what it takes to be a Tier 1 supplier, and it is the role Nano-C has built itself to play for perovskite-silicon tandem production.
Scale. Founded in 2001 from research at MIT, Nano-C has spent more than two decades manufacturing fullerenes and other carbon-based materials for semiconductor, energy-storage and photovoltaic customers. Its proprietary continuous fullerene synthesis process was built for commercial procurement rather than research-scale sampling, with capacity that can expand as customers move from pilot lines to gigawatt-scale deployment. Nano-C is now scaling to multi-ton production.
Purity. In an ETL, purity is a key performance parameter. Trace impurities can increase non-radiative recombination, and batch-to-batch variation can quietly erode yield. Nano-C supplies C60 in multiple grades, including a sublimed grade exceeding 99.95% purity, and work with industrial and research partners has shown improved batch repeatability compared with lower-purity alternatives.
Control. Nano-C is the only fully vertically integrated manufacturer of fullerene, single-walled carbon nanotube and synthetic organic materials serving the photovoltaic sector. Synthesis, purification, separation, derivatization and formulation all happen under one roof, giving customers complete traceability and a single point of technical accountability. In May 2026, the company achieved ISO 9001:2015 certification for the quality management systems that underpin this production.
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The Second Clock: Research on the Next Generation
Tandem commercialization runs on two clocks. The production clock is about making today's proven stack reliably and in volume. The research clock is about the materials that will push efficiency and lifetime further over the next five to ten years, and it is moving just as fast. Nano-C works on both, supplying volume materials to manufacturers while collaborating with leading corporate and academic research groups on next-generation devices.
Several directions attract particular interest:
Fixing the fullerene interface. Solution-processed fullerene derivatives bearing phosphonic acid or ammonium salts, such as Nano-C's mono- and bis-FAPA, are designed to bind more strongly at the interface, suppressing recombination and ion migration while addressing the adhesion weakness of a bare C60 layer. Nano-C also supplies C[60]PCBM.
Better hole contacts. SAM HTLs such as 0PATPA and Ph4PACz have been central to recent efficiency gains. Cross-linkable HTLs now in development by Nano-C aim to add processing robustness and stability, which matter as much on a production line as peak efficiency does.
Looking beyond C60. C70 offers a different combination of optical and electronic properties from C60. Because the two are produced together, rising C60 demand is improving the economics of high-purity C70, making it practical for device developers to evaluate technical merit in applications where even a marginal ETL gain improves system-level economics.
Taking indium out of the stack. Tandem cells typically rely on indium-based transparent electrodes, and indium supply is a recognized concern as solar heads toward terawatt-scale deployment. While Nano-C's primary focus remains ETLs, HTLs and interface engineering materials, the company is also investing in transparent conductor technologies. Its Invisicon® platform utilizes single-walled carbon nanotube and nanowire technologies to provide an indium-free alternative to conventional transparent electrodes, offering compatibility with spray coating, inkjet printing and roll-to-roll manufacturing processes.
The race to scale the foundational materials for near term and medium term are tied together. Fullerene derivatives are built from the same C60 and C70 that go into today's production ETLs, so a next-generation material developed in the lab can draw on a supply chain that is already running at commercial scale. That shortens the path from a promising result in a research paper to a material a manufacturer can qualify, and it is why Nano-C treats research partnership and volume manufacturing as a single strategy rather than two.
Looking Ahead
As perovskite technologies move towards large-scale deployment, attention is increasingly focused on stability, lifetime and manufacturing robustness. Nano-C's innovation strategy is centered on high-value interfaces, where material selection can have a significant impact on device performance and reliability.
The next few years will test perovskite-silicon tandems in ways that efficiency records cannot: through processing yields and field data. The manufacturers that succeed will treat their materials supply chain with the same rigour as their equipment and processes. And because so much of the remaining performance headroom sits at the interfaces, the next generation of records is likely to be won in those same few nanometres.
To discuss Nano-C's perovskite solar materials, request technical information or arrange samples, visit booth P04 or contact Nano-C through Nano-C.com.
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