Public defence in Engineering Physics, M.Sc. Azimatu Fangnon

As we evolve technologically, the surge in our energy demands also escalates. Currently, fossil fuel is the largest source of energy. However, it is unsustainable and a major contributor to green house effect. In order to meet these huge energy demands, there is the need to search for more sustainable, affordable and environmentally friendly energy sources. Of all the renewable energy sources, solar energy is the most promising due to the large amount of solar radiations reaching the surfaces of the earth. To advance solar energy as a primary source of energy, there is the need to investigate materials that are sustainable and affordable with the ability to harness enough of the solar radiations. Perovskites, after a decade of their discovery as solar cell materials, have shown potential to advance solar cell technology.

The subject of this study is to define a modeling protocol for an efficient and stable perovskite solar cells (PSCs). Perovskite materials have been identified to yield high power conversion efficiency (PCE) comparable to that of silicon-based solar cells. They are also affordable, sustainable and easy to fabricate at low temperatures. However, these promising solar cell materials suffer from degradation when exposed to ambient conditions such as moisture, excessive heat and oxygen. In this thesis, I outline a modeling protocol that is aimed at protecting the surfaces of perovskites from such ambient conditions through protective coating without compromising its PCE. The study includes identifying potential coatings, understanding the perovskite surfaces and perovskite-coating interfaces. My work shows inorganic materials beyond the commonly known metal oxides with the tendency to protect and also serve as charge transport materials for PSCs. In the surface studies, I found stable reconstructed surface models in addition to the traditional "clean surface terminated" models. Both the surface and perovskite-coating interface studies showed no mid-gap states. This result is actually good since such mid-gap states could lead to non-radiative charge recombination which may hinder the PCE. Another interesting result is how the properties of the coatings change at the interface. The findings from this work serve as a starting point for future work on surface adsorbates, defects and interface engineering of PSCs.

Opponent is Associate Professor Cesare Franchini, University of Vienna, Austria

Custos is Professor Patrick Rinke, Aalto University School of Science, Department of Applied Physics

Contact details of the doctoral student: [email protected], +358465415234

The public defence will be organised in Otaniemi (Ekonominaukio 1, lecture hall V002) and via Zoom. Link to the event

The dissertation is publicly displayed 10 days before the defence in the publication archive Aaltodoc of Aalto University

Electronic thesis