China makes them almost as efficient as silicon ones

For years, polymer solar cells (popularly known as organic or “plastic” plates) have promised a real revolution in the renewable energy sector. Being light, flexible and even printable, their potential seemed limitless. However, in practice they had a big Achilles heel: they degraded quickly when exposed to air and their capacity to generate energy was far below that of the classic and heavy silicon panels. They were, in the eyes of the industry, almost a laboratory toy.

But this narrative has just taken a historic turn. A team of scientists has managed to simultaneously overcome the barrier of performance and degradation, finally bringing these flexible plates closer to their long-awaited large-scale commercialization.

A milestone that comes from China. Until today, manufacturing flexible solar panels meant taking a toll: either you lost efficiency or the material degraded quickly in the open air. Researchers at Wuhan University of Technology just broke that rule. Its new polymer cell reaches an efficiency of 19.1% – close on the heels of commercial silicon – and, above all, solves the problem of wear.

As endorsed by the scientific journal Matterthe device supports more than 2,000 hours of outdoor operation while retaining 97% of its initial capacity. In technical jargon, they have achieved a “T97 lifetime”, a metric that definitively takes this technology out of the experimental phase.

The step definitive towards marketing. In statements to the magazine PV MagazineTao Wang, co-author of the research, highlights the magnitude of the finding: the stability demonstrated in these 2,000 hours allows us to extrapolate a useful life of the device that would exceed 100,000 hours of operation.

Furthermore, this breakthrough puts an end to organic photovoltaics’ historic dilemma of the war between “efficiency vs. stability.” As the research points out, until now polymers (formed by long molecular chains) were very thermally stable and flexible, but inefficient; On the contrary, the “small molecules” were more efficient but too fragile and tended to crystallize over time, ruining the plate. This new development manages to combine the best of both worlds.

The “invisible comb” at the microscopic level. Therein lies the secret of its success. Wei Li, another of the study’s lead authors, explains in PV Magazine that polymers have a mechanical problem: their long molecular chains tend to tangle, forming “disordered aggregates.” That disorder not only blocks the flow of electricity (reducing efficiency), but it exposes weak chemical bonds that accelerate the degradation of the board in sunlight.

To solve this, the Wuhan team applied a strategy that was as elegant as it was effective: they introduced a small fraction of “small acceptor molecules” (SMA) into the polymer matrix. According to the study, this mixture acts as an invisible comb that “untangles” the long chains of the polymer, forcing them to pack in a linear and orderly manner. This reduces empty spaces in the material, creating direct “highways” for electricity to flow without being lost, boosting efficiency and stopping photochemical deterioration in its tracks.

A high-tech “sandwich”. For this chemical cocktail to work, the design of the plate was not left to chance. The cell was literally built like a sandwich on a microscopic scale. Instead of complicated heavy metal alloys, they used a transparent base on which they applied several ultrathin layers: one that captures light (the improved polymer), others that act as guides so that electrons do not escape and, finally, a very thin layer of silver to conduct electricity. The whole set results in a high precision, but extremely light device.

And what does all this mean for the average user? According to the portal Interesting Engineeringthese findings pave the way to integrate highly efficient panels into tents, backpacks, clothing or covering the curved facades of buildings, without having to support the immense weight of silicon.

This vision of the future is already taking its first commercial steps. As we saw a year ago at CES, brands like Anker Solix are already experimenting with prototypes of jackets that integrate solar panels and power banks to keep a cell phone charged, or beach umbrellas capable of charging a portable refrigerator using continuous photovoltaic cells. The difference is that, thanks to the new molecular advances achieved in China, this “wearable” and portable self-consumption technology will take a brutal leap: it will be much more stable, durable and easier to mass produce.

The future is already flexible. The absolute hegemony of silicon – rigid, heavy and with a high manufacturing energy cost – is beginning to have a real alternative on the horizon. Research from Wuhan University of Technology shows that understanding and manipulating how molecules behave and intertwine was the master key to getting organic technology out of the laboratory. The future of solar energy no longer only seeks to be efficient; Now it is ready to be flexible, ultralight and, finally, durable.

Image | RawPixel

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