Sannino, Gennaro Vincenzo (2024) Rational Design of Charge Transport Materials and Interfaces for Perovskite Solar Cells. [Tesi di dottorato]

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Abstract

Throughout my Ph.D., we have explored various aspects of charge transport materials and interfaces in perovskite solar cells, employing both experimental and computational approaches. A significant part of our research has been focused on tin dioxide (SnO2), a promising electron transport material that, over the years, has emerged as the current benchmark for the electron transport layer (ETL) in perovskite solar cells (PSCs) with n-i-p architecture. We have conducted comprehensive research on this material, presenting different approaches to enhance its ETL features and providing computational density functional theory (DFT) studies that explain experimental observables from an atomistic perspective. A novel PPS additive has been proposed for preparing SnO2 QDs solutions, significantly reducing hysteresis phenomena within the fabricated PSCs. We have investigated the performance of ETLs composed of SnO2 composites with other metal oxides. A computational study regarding different doping concentrations of Mg in SnO2 has revealed new insights on the trend of VOC values observed in experiments. Finally, a thorough investigation into the effects generated by oxygen vacancies has enabled us to develop a valuable model tailored for predicting the conduction band minimum of the SnO2. The other part of the research involves manipulating the perovskite interface using interfacial layers. In this case as well, we have employed both experimental and computational approaches to discern various properties crucial in evaluating the interface quality. We have proposed the engineering of the CsPbI3 surface by simultaneously employing both TOPO and OAI molecules, resolving the unfavourable downward band bending induced by OAI passivation and, consequently, improving the energy level alignment between the perovskite and the Spiro-OMeTAD. Moreover, we have investigated the role played by an atom-thin NaCl layer on top of the MAPbI3 perovskite through DFT calculations. We have found modifications in the valence and conduction band positions of the perovskite, along with its ability of reducing defect formation. In definitively, through a combination of experimental and theoretical studies, we have explored the pivotal roles played by the morphology of the CTL, the alignment of energy levels, and the passivation of defects at the interface. These new insights, combined with a deeper understanding of the mechanisms driving these enhancements, contribute to the advancement process of the PSC technology.

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