Towards More Efficient Solar Cells: the Effect of Dynamical Disorder on the Electronic Structure of Halide Double Perovskites
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Examensarbete för masterexamen
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Modellbyggare
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Sammanfattning
Recently, simple perovskites have attracted great attention as energy-absorbing materials
in solar cells. In computational and experimental studies they have shown
several desirable properties but also challenges, such as instabilities and toxicity due
to the presence of heavy metals, such as lead. As a solution to the problems connected
to the simple perovskites, the double perovskites were suggested as suitable
materials in the solar cells of tomorrow. In order to use double perovskites in an
application they need to be thoroughly understood. Within this thesis the octahedral
tilting and the band gap of double perovskites have been studied, which is a
step towards finding a material that is stable and exhibit the optimal band gap for
absorbing solar energy. It turns out that the octahedral tilting is not as prominent
in all double perovskites as in the simple ones. The statement that the octahedral
tilting is due to the presence of lone-pair electrons is considered and it agrees with
the calculations - lone-pair electrons induce octahedral tilting. The effect of octahedral
tilting on the band gap of the double perovskites is studied as well and it is
concluded that the band gap increases with the tilting. So, as the global warming
increases rapidly it is important to find green solutions and as solar cells produce
renewable energy and are emission-free they are good candidates for further research
and developement.
Beskrivning
Ämne/nyckelord
perovskites, band gap, DFT, VASP, solar cells, phonons, lone-pair electrons, octahedral tilting