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Tuning perovskite solar cells with nanoparticle additives

(Nanowerk News) Researchers have employed carbon nanoparticles with an average diameter of 20 nm in high efficiency state-of-the-art perovskite solar cells to control the morphology of the perovskite film.
Recently, perovskite solar cells have attracted considerable interest among the photovoltaics research community, because of their high solar-to-electric power conversion efficiencies and low fabrication costs.
In new work, reported in Advanced Energy Materials ("Carbon Nanoparticles in High-Performance Perovskite Solar Cells"), an international research team has for the first time, carbon nanoparticles (CNPs) containing functional groups have been incorporated in perovskite solar cells.
Carbon nanoparticles
Carbon nanoparticles. a) Top SEM image, b) size distribution curve, c) UV–vis absorbance and photoluminescence spectra of CNPs in DMF:DMSO 4:1 for 375 and 400 nm excitation wavelengths, and d) IR spectra of CNPs. (© Wiley-VCH Verlag) (click on image to enlarge)
"we find that the functional groups of the CNPs interact with perovskite components already in the precursor solution resulting in a larger grain size, better thermal stability, and hydrophobicity of the perovskite film," write the scientists. "Whereas efficiencies above 18% could be maintained after adding the CNPs, the hysteresis in the current–voltage curves was considerably decreased compared to reference devices."
The films show larger grain sizes and increased thermal stability when CNPs were added to the perovskite by dispersing them in the precursor solution.
Whereas a power conversion efficiency larger than 18% could be maintained, the hysteresis was decreased to negligible values despite using a TiO2 contact.
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Different perovskite solutions image and device schematic. a) CsM perovskite solution (left) and the CsM/0.08CNP solution (right), crosssectional SEM images of b) CsM and c) CsM/0.08CNP solar cells and d) schematic of full perovskite solar cell. (© Wiley-VCH Verlag)
Films containing CNPs were found to be more hydrophobic. NMR analyses showed that hydrogen bonds are formed between formamidinium cations and functional groups of CNPs already in solution.
"This study shows that additives are a promising path toward morphology tuning and increasing thermal stability," the authors conclude.
Michael Berger By – Michael is author of three books by the Royal Society of Chemistry:
Nano-Society: Pushing the Boundaries of Technology,
Nanotechnology: The Future is Tiny, and
Nanoengineering: The Skills and Tools Making Technology Invisible
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