High stability perovskite for solar cells

High stability perovskite for solar cells

Technology News |
By Nick Flaherty

Researchers in the US have developed a perovskite material that provides high efficiency and longer lifetime for photovoltaic solar cells.

The researchers at Rice University found a way to synthesize formamidinium lead iodide (FAPbI3) for the highest-efficiency perovskite solar cells with higher stability.

This is important for flexible solar cells as well as tandem PV panels that have a perovskite layer on top of silicon cells to capture more of the energy from the sun for higher conversion efficiency.

The 2D-templated bulk FAPbI3 films exhibited an efficiency of 24.1% in a p-i-n architecture with 0.5–square centimetre active area and an exceptional durability, retaining 97% of their initial efficiency after 1000 hours under 85°C and maximum power point tracking.

Metal halide perovskite process boosts solar cell lifetime

“Right now, we think that this is state of the art in terms of stability,” said Rice engineer Aditya Mohite. “Perovskite solar cells have the potential to revolutionize energy production, but achieving long-duration stability has been a significant challenge.”

The material is also market-ready. The key was “seasoning” the FAPbI3 precursor solution with a sprinkling of specially designed two-dimensional (2D) perovskites. These served as a template guiding the growth of the bulk/3D perovskite, providing added compression and stability to the crystal lattice structure.

“Perovskite crystals get broken in two ways: chemically ⎯ destroying the molecules that make up the crystal ⎯ and structurally ⎯ reordering the molecules to form a different crystal,” said Isaac Metcalf, a Rice materials science and nanoengineering graduate student and a lead author on the study. “Of the various crystals that we use in solar cells, the most chemically stable are also the least structurally stable and vice versa. FAPbI3 is on the structurally unstable end of that spectrum.”

The researchers developed four different types of 2D perovskites ⎯ two with a surface structure nearly indistinguishable from that of FAPbI3 and two less well-matched ⎯ and used them to make different FAPbI3 film formulations.

“The addition of well-matched 2D crystals made it easier for FAPbI3 crystals to form, while poorly matched 2D crystals actually made it harder to form, validating our hypothesis,” Metcalf said. “FAPbI3 films templated with 2D crystals were higher quality, showing less internal disorder and exhibiting a stronger response to illumination, which translated as higher efficiency.”

Upscaling production of perovskite solar panels

The 2D crystal templates improved not only the efficiency of FAPbI3 solar cells but also their durability. While solar cells without any 2D crystals degraded significantly after two days of generating electricity from sunlight in air, solar cells with 2D templates did not start degrading even after 20 days. By adding an encapsulation layer to the 2D-templated solar cells, stability was further improved to timescales approaching commercial relevance.

“Perovskites are soluble in solution, so you can take an ink of a perovskite precursor and spread it across a piece of glass, then heat it up and you have the absorber layer for a solar cell,” Metcalf said. “Since you don’t need very high temperatures ⎯ perovskite films can be processed at temperatures below 150 Celsius (302 Fahrenheit) ⎯ in theory that also means perovskite solar panels can be made on plastic or even flexible substrates, which could further reduce costs.”

“It should be much cheaper and less energy-intensive to make high-quality perovskite solar panels compared to high-quality silicon panels, because the processing is so much easier,” said Metcalf.

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