Probing the Chemical Instability of the Perovskite/MoO3 Interface via Precursor Studies

Sofia Apergi^a^,^b, Christine Koch^c, Geert Brocks^a^,^b^,^d, Selina Olthof^c, Shuxia Tao^a^,^b

^aMaterials Simulation and Modelling, Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands

^bCenter for Computational Energy Research, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, Eindhoven, Netherlands

^cDepartment of Chemistry, University of Cologne, Greinstraße 4-6, 50939 Cologne, Germany

^dComputational Materials Science, Faculty of Science and Technology and MESA+, Institute for Nanotechnology, University of Twente, Enschede, The Netherlands

International Conference on Hybrid and Organic Photovoltaics
Proceedings of 13th Conference on Hybrid and Organic Photovoltaics (HOPV21)

Online, Spain, 2021 May 24th - 28th

Organizers: Marina Freitag, Feng Gao and Sam Stranks

Oral, Sofia Apergi, presentation 043
Publication date: 11th May 2021

Despite the rapid progress in perovskite solar cells (PSCs), their commercialization is still prohibited by various issues, with the most critical one being their instability. Part of the cause, and therefore the solution, lies at the charge selective contacts and their interfaces with halide perovskites. With MoO3 being one of the most successful hole transport layers in organic photovoltaics, the disastrous results of its combination with MAPbI3 came as a surprise but was later attributed to severe chemical instability at the MoO3/MAPbI3 interface. To discover the atomistic origin of this instability, we used density functional theory (DFT) calculations to investigate the interaction of MoO3 with perovskite precursors, which is the starting point of the formation of the interfaces. Besides MAPbI3 we also extended the study to FA and Br compositions. Two possible degradation routes leading to halogen oxidation and Mo reduction were identified, which are triggered by oxygen vacancies on the MoO3 surface. Iodine was found to be especially reactive, in contrast to Br, which does not significantly affect the oxide. These results were confirmed by XPS measurements revealing severe reduction of MoO3 accompanied by loss of iodine, when the oxide is interfaced with I-containing precursors. Based on these results, we can conclude that by avoiding I or applying interface passivation MoO3 could be employed as an effective HTL in PSCs and other perovskite optoelectronic devices, such as LEDs.

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International Conference on Hybrid and Organic Photovoltaics

International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.

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