Theoretische Vorhersagen der Struktur und der optischen und elektronischen Eigenschaften zweidimensionaler organisch-anorganischer Perovskit-Hybridverbindungen für potentielle Anwendung in Leuchtdioden
Zusammenfassung der Projektergebnisse
Hybrid organic-inorganic materials combine the properties of organic and inorganic substances at the nanoscale, like e.g. high chemical tunability vs. high electric mobility. Especially hybrid organic-inorganic perovskites (HOIP) have recently received increasing attention due to their promising properties for application in photovoltaic (PV) devices or, e.g. light emitting diodes (LED). To determine computationally if a hybrid material might be suited for LED or PV application, its atomic structure needs to be modeled accurately. Based on the atomic structure, its electronic structure can be modeled to investigate how the hybrid material might absorb or emit light and if charge carriers could be transferred between the organic and inorganic component so that both the properties of organic and inorganic can be exploited. My research dealt with computational atomic and electronic structure prediction and investigation pf hybrid organic-inorganic materials. In collaboration with the group of Dr. Spano at Temple University, a model Hamiltonian was applied to two-dimensional HOIPs (2D HOIPs) to describe the light absorption spectra of the organic component. This model had been previously developed to describe how materials made from organic molecules absorb and emit light. In our research, we showed that the model Hamiltonian can be used to relate changes in the underlying molecular arrangement to changes in the organic contribution to the HOIP absorption spectra. This work represents the first step towards a broader model Hamiltonian that could allow treatment of both the organic and inorganic contribution to absorption and emission spectra. When finalized, the broader model Hamiltonian could be combined with machine learning to help identify potential 2D HOIPs for LED or PV application. Originally, I proposed to develop an algorithm to predict the atomic structure of new 2D HOIPs, and to simulate their electronic structure. Arising from an ongoing collaboration with the Fritz Haber Institute in Berlin, we investigated the electronic structure at the organic-inorganic interface of the tetracene (Tc) or pentacene (Pc) with hydrogenated silicon (H/Si(111)) to see if charges could in principle be transferred from the molecular films to the inorganic surface. The system is of particular interest, because singlet fission materials like Tc and Pc allow to create two charge carriers out of a high energy excitation, e.g. light. If fission materials could be combined with Si, the efficiency of traditional Si PV devices could potentially be improved. We developed a computational protocol that allowed to predict a sensible interface structure between a Tc or Pc monolayer film and a H/Si(111) surface based on the structure of the isolated film and surface. Based on computationally highly challenging hybrid density functional theory calculations of the electronic structure, we concluded that for Tc or Pc films on H/Si(111), only electrons, but not holes, can in principle be transferred from the film to the substrate. Finally, I participated in collaborations with experimental co-workers about replacement of toxic lead in 2D HOIPs and tunability of 2D HOIP electronic structure properties by choice of different organic components. To these, I contributed by either performing or working with Ph.D. students on density functional theory calculations of the atomic and electronic structure properties of 2D HOIPs. These calculations supported the interpretation of experimental observations and resulted in two publications in Nature Chemistry and J. Am. Soc. Chem., which have been subject to or mentioned in press releases. In conclusion, I have taken first steps towards a model Hamiltonian for description of absorption and emission spectra in 2D HOIPs and suggested a protocol for computational investigation of electronic structure at hybrid organic-inorganic interfaces. Overall, through my research I have contributed to the understanding of atomic and electronic structure in hybrid organic-inorganic materials.
Projektbezogene Publikationen (Auswahl)
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J. Am. Chem. Soc., 141, 7955 (2019)
Manoj K. Jana, Svenja M. Janke, David J. Dirkes, Seyitliyev Dovletgeldi, Chi Liu, Xixi Qin, Kenan Gundogdu, Wei You, Volker Blum and David B. Mitzi
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Nature Chemistry 11, 1151 (2019)
Yao Gao, Enzheng Shi, Shibin Deng, Stephen B. Shiring, Jordan M. Snaider, Chao Liang, Biao Yuan, Ruyi Song, Svenja M. Janke, Alexander Liebman-Peláez, Pilsun Yoo, Matthias Zeller, Bryan W. Boudouris, Peilin Liao, Chenhui Zhu, Volker Blum, Yi Yu, Brett M. Savoie, Libai Huang and Letian Dou
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J. Chem. Phys. 152, 144702 (2020)
Svenja M. Janke, Mohammad B. Qarai, Volker Blum and Frank C. Spano
