.S. scientists have set a new record in solar energy, achieving an efficiency rate of 25.1% for large-area perovskite-silicon tandem solar cells. This big step could make solar production cheaper and decrease energy losses, putting it on track to outpace traditional solar tech for business and industry settings.

While crystalline silicon has been the main ingredient in solar panels for a long time, it isn't exactly the champion in terms of efficiency. Perovskite has emerged as a highly efficient alternative, which excels at light absorption but struggles with durability. To combine the best of both worlds, scientists have developed tandem cells, stacking perovskite atop silicon. On a small scale, these combined cells have already hit conversion rates of over 30%, but increasing their size without compromising efficiency has been a hurdle.

In their latest study, researchers from the University of North Carolina at Chapel Hill focused on overcoming a major obstacle in scaling up perovskite-silicon solar technology - the unpredictable nature of perovskites on large surfaces. This often leads to "shunting," a phenomenon that creates alternative electrical pathways, diverting current and lowering the cell's performance.

To tackle this issue, the researchers experimented with three types of silicon base layers: mechanically polished float zone (FZ) cells, potassium-hydroxide-etched Czochralski silicon cells (etched CZ), and textured surface Czochralski silicon cells (textured CZ). While all three demonstrated comparable efficiencies in smaller configurations, the etched CZ bottom cells outperformed the rest when it came to scaling.

The game-changing move in the research was the addition of a 2nm-thick lithium fluoride (LiF) interlayer. Placed between a poly-triarylamine (PTAA) hole transport layer and a wide bandgap perovskite absorber, this LiF sheet served as a safeguard against shunting. It helped improve the overall connectivity within the cell, minimized energy loss, and was a key player in achieving a record-setting 25.1% efficiency rate in the 24-square-centimeter solar cell.

According to the research team, "The strategy developed here is valuable for developing efficient, reproducible, and large-scale perovskite-silicon tandems." Though there is still progress to be made, this study's outcomes are a clear win for the future of making solar power more efficient.



Nov 27, 2023

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