| Aug 11, 2025 |
New coating improves thermal stability of flexible perovskite solar devicesLead-free coating improves heat stability and durability of flexible perovskite solar cells for portable and building-integrated applications. |
| (Nanowerk Spotlight) Thin, lightweight solar cells that can bend and flex open the door to power sources built into clothing, curved surfaces, and portable devices. But flexibility comes at a cost. Under strong sunlight, surfaces can heat up, and in flexible perovskite solar cells that heat can quickly damage the light-absorbing layer. Once the crystal structure begins to break down, performance drops and the device’s useful life shortens. |
| Perovskites are a family of materials known for their high light absorption and low-cost processing. They have shown promise for flexible photovoltaics. Yet their sensitivity to heat and environmental stress has slowed progress toward real-world use. Conventional stabilizing additives often contain lead or other toxic elements, raising environmental concerns. |
| Researchers from Nanjing University of Posts and Telecommunications and collaborators have found a way to make flexible perovskite solar cells more resistant to heat without using hazardous additives. Their method adds a thin, lead-free protective layer that strengthens the perovskite against thermal stress while keeping efficiency high. |
| The findings have been published in Advanced Energy Materials ("Environmentally Friendly Flexible Perovskite Solar Cells with Promoted Thermal Diffusivity and Suppressed Lead Leakage"). |
| The team uses potassium hexafluorotitanate, or K₂TiF₆, a compound containing potassium and titanium but no heavy metals. When applied to the perovskite surface, it bonds with the crystal and fills in defect sites — small imperfections that can trap charges and allow moisture or oxygen to penetrate. By passivating these defects, the coating makes the perovskite more stable under heat. |
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| a) Infrared thermal imaging during the thermal annealing of the perovskite thin films. PL mapping images of the b) control and c) target perovskite thin films. d) Time-resolved PL decay spectra. Top-view SEM images of the e) control and f) target perovskite thin films. High-resolution TEM images of the g) control and h) target perovskite thin films. (Image: Reprinted with permission by Wiley-VCH Verlag) (click on image to enlarge) |
| Flexible perovskite films are typically prepared from solutions, which can leave behind solvent residues and uneven crystal edges. These imperfections can change under heat, disrupting the material’s structure. The K₂TiF₆ treatment reduces these weak points, keeping the crystal lattice intact for longer periods. |
| The researchers built flexible solar cells on polyethylene naphthalate, a plastic substrate that tolerates processing temperatures but can bend without damage. They compared untreated cells with those treated using K₂TiF₆. Both started with similar efficiencies, but after prolonged storage at 85 degrees Celsius, the treated devices retained much more of their initial performance. |
| Tests showed that the treatment also reduced ion migration — the movement of charged atoms or molecules within the perovskite layer. Ion migration can shift the internal structure and cause gradual performance loss. Measurements using X-ray diffraction and spectroscopy confirmed that the protective layer slowed these changes. |
| Mechanical flexibility was unaffected by the treatment. The coated devices endured repeated bending with minimal loss in output, meeting a core requirement for wearable and portable applications. Because the method relies on a simple coating step and a widely available, non-toxic compound, it could be integrated into scalable manufacturing. |
| The researchers note that their approach could be combined with other stabilizing strategies, such as encapsulation layers or mixed-cation perovskite compositions, to further extend device lifetimes. Using a benign additive also helps lower the environmental footprint of perovskite technology, which is a priority for commercial adoption. |
| This work highlights how targeted surface engineering can address one of the main weaknesses of flexible perovskite solar cells. By adding a thin, lead-free coating that protects against heat-induced degradation, the team has advanced the durability of a technology poised for applications ranging from rollable solar panels to integrated building materials. |
By
Michael
Berger
– Michael is author of four books by the Royal Society of Chemistry:
Nano-Society: Pushing the Boundaries of Technology (2009),
Nanotechnology: The Future is Tiny (2016),
Nanoengineering: The Skills and Tools Making Technology Invisible (2019), and
Waste not! How Nanotechnologies Can Increase Efficiencies Throughout Society (2025)
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