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Physics of Interfaces in MAPbI3 Perovskite Solar Cells

An, Qingzhi

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Abstract

Interfaces in perovskite solar cells, such as interfaces between adjacent layers or at grain bound- aries, play an important role in determining the performance of photovoltaic devices. This thesis describes investigations of the physical properties of several such interfaces in order to elucidate their influence on the photovoltaic devices and further utilize this knowledge to improve the device performance. First, we investigate the interface between a perovskite active layer and a ZnO elec- tron transport layer. We demonstrate that this interface strongly influences the microstructure of polycrystalline perovskite. Using a combination of doping and modification by a self-assembled monolayer, we optimize both the bulk and surface properties of the ZnO layer, leading to a su- perior perovskite layer microstructure and a doubling of the photovoltaic performance. Next, we investigate the interface between an organic electron transport layer and the metal cathode. We modify this interface by inserting a series of newly synthesized π -extended phosphoniumfluorene electrolytes and demonstrate that such modification significantly increases the built-in potential of the device by compensating for the non-ideal energetic alignment caused by the other device layers. Consequently, the modified devices exhibit an increase in the open-circuit voltage by up to 120 mV. Finally, we systematically investigate the effects of grain boundaries on the performance of perovskite solar cells by combining the experimental characterizations and the theoretical de- vice simulations. We show that grain boundaries contribute to the non-radiative recombination losses in perovskite solar cells and the small grains serve as recombination ’hot spots’ that limit the open circuit voltage, as well as the performance of the devices.

Item Type: Dissertation
Supervisor: Vaynzof, Prof. Dr. Yana
Place of Publication: Heidelberg
Date of thesis defense: 10 December 2020
Date Deposited: 15 Dec 2020 14:58
Date: 2020
Faculties / Institutes: The Faculty of Physics and Astronomy > Kirchhoff Institute for Physics
Subjects: 530 Physics
Controlled Keywords: Perovskite Photovoltaics
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