Development of antimony-based perovskite-inspired solar cells
Lamminen, Noora (2022)
Lamminen, Noora
2022
Master's Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2022-01-28
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202201241553
https://urn.fi/URN:NBN:fi:tuni-202201241553
Tiivistelmä
One of the most important challenges to fight climate change is finding alternative clean energy production methods. In just more than a decade, perovskite has become the most promising and efficient emerging photovoltaic material. Halide perovskites are materials with an ABX3 crystal structure, where A is a monovalent (often organic) cation, B is a metal cation, and X is a halogen anion or a mixture of several halogen anions. The most efficient halide perovskites have a mixture of organic and inorganic cations as the A site and a lead Pb2+ cation in the B site. However, because lead is toxic there is a need to find new lead-free alternatives. One safer alternative to lead is antimony (Sb).
This work focused on the fully inorganic perovskite-inspired material Cs3Sb2I9. It can be made in two different crystal structures 0D and 2D. Of these, the 2D structure is more suited to solar cell applications. The 2D structure has been difficult to obtain and in the past, strong acids like HCl and HI and high temperatures have generally been needed. In this work, the 2D structure was achieved with the use of an ammonium salt, namely methylammonium chloride. It is widely adopted in perovskite research and is easy to handle inside a nitrogen-filled glovebox. The other interest of this work was to improve the solar cell efficiency by forming the first hybrid organic-inorganic cesium antimony perovskite-inspired material with the structure Cs3−xFAxSb2I9. This was done by partly replacing cesium iodide (CsI) with formamidinium iodide (FAI) in the precursor solution of the perovskite-inspired material.
Most efficient devices contained 20% and 50% of FA in the total A cation amount. The perovskite-inspired material thin films were characterized with electron microscopy, spectroscopy, and X-ray diffraction and tested in solar cells. With the Cs3Sb2I9 perovskite-inspired material the highest solar cell efficiency of 1.2% was reached. Partial substitution of Cs with FA improved the efficiency of the solar cells, yielding 2.3% power conversion efficiency. In conclusion, this work provided a new, fast, and safe method of forming the preferred 2D crystal structure of Cs3Sb2I9. In addition, the same method was successfully employed to synthesize a new hybrid Cs3−xFAxSb2I9 material which significantly improved the solar cell efficiency compared to the fully inorganic Cs3Sb2I9. This work highlights the importance of developing new lead-free perovskite-inspired compositions, as well as film engineering methods, to enable solar cells with ever-growing efficiency.
This work focused on the fully inorganic perovskite-inspired material Cs3Sb2I9. It can be made in two different crystal structures 0D and 2D. Of these, the 2D structure is more suited to solar cell applications. The 2D structure has been difficult to obtain and in the past, strong acids like HCl and HI and high temperatures have generally been needed. In this work, the 2D structure was achieved with the use of an ammonium salt, namely methylammonium chloride. It is widely adopted in perovskite research and is easy to handle inside a nitrogen-filled glovebox. The other interest of this work was to improve the solar cell efficiency by forming the first hybrid organic-inorganic cesium antimony perovskite-inspired material with the structure Cs3−xFAxSb2I9. This was done by partly replacing cesium iodide (CsI) with formamidinium iodide (FAI) in the precursor solution of the perovskite-inspired material.
Most efficient devices contained 20% and 50% of FA in the total A cation amount. The perovskite-inspired material thin films were characterized with electron microscopy, spectroscopy, and X-ray diffraction and tested in solar cells. With the Cs3Sb2I9 perovskite-inspired material the highest solar cell efficiency of 1.2% was reached. Partial substitution of Cs with FA improved the efficiency of the solar cells, yielding 2.3% power conversion efficiency. In conclusion, this work provided a new, fast, and safe method of forming the preferred 2D crystal structure of Cs3Sb2I9. In addition, the same method was successfully employed to synthesize a new hybrid Cs3−xFAxSb2I9 material which significantly improved the solar cell efficiency compared to the fully inorganic Cs3Sb2I9. This work highlights the importance of developing new lead-free perovskite-inspired compositions, as well as film engineering methods, to enable solar cells with ever-growing efficiency.