Computational multi-scale model for the structure of hybrid perovskites : Analysis of charge migration in novel photovoltaic materials

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http://urn.fi/URN:NBN:fi-fe201804208544
Julkaisun nimi: Computational multi-scale model for the structure of hybrid perovskites : Analysis of charge migration in novel photovoltaic materials
Tekijä: Järvi, Jari
Muu tekijä: Helsingin yliopisto, Matemaattis-luonnontieteellinen tiedekunta, Fysiikan laitos
Julkaisija: Helsingin yliopisto
Päiväys: 2018
Kieli: eng
URI: http://urn.fi/URN:NBN:fi-fe201804208544
http://hdl.handle.net/10138/273522
Opinnäytteen taso: pro gradu -tutkielmat
Oppiaine: Theoretical Physics
Teoreettinen fysiikka
Teoretisk fysik
Tiivistelmä: Hybrid organic-inorganic perovskites (HPs) are a novel materials class in photovoltaic (PV) power generation. The PV performance of HPs is impressive, although the microscopic origin of it is not well known due to the complex atomic structure of HPs. Specifically, the disordered mobile organic cations aggravate the use of conventional computational models. I have addressed this structural complexity by developing a multi-scale model that applies quantum mechanical (QM) calculations of small HP supercell models in large coarse-grained structures. With a mixed QM-classical hopping model, I have studied the effects of cation disorder on charge mobility in HPs, which is a key feature to optimize their PV performance. My multi-scale model parametrizes the interaction between neighboring methylammonium cations (MA) in the prototypical HP material, methylammonium lead triiodide (CH3NH3PbI3, or MAPbI3). For the charge mobility analysis with my hopping model, I solved the QM site-to-site hopping probabilities analytically and computed the nearest-neighbor electronic coupling energies from the band structure of MAPbI3 with density-functional theory. I investigated the charge mobility in various MAPbI3 supercell models of ordered and disordered MA cations. My results indicate a structure-dependent mobility, in range of 50–66 cm2/Vs, with the highest observed in the ordered tetragonal phase. My multi-scale model enables the study of long-range atomistic processes in complex structures in an unprecedented scale with QM accuracy, with potential applications way beyond this study.


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