(Invited) A First-Principles Study on Photoinduced Hole Injection into Organic Molecule on Metal Halide Perovskite Surface

Tuesday, 30 May 2017: 10:40
Churchill C1 (Hilton New Orleans Riverside)
M. Sugimoto (Kumamoto University)
The perovskite solar cell (PSC) is one of the emerging photovoltaic devices with rapid enhancement of the energy conversion efficiency. For further improvement, versatile efforts have been made to uncover important factors determining to the device performance. In particular, carrier injection across material interfaces in the device is considered to be the most critical electronic process.

In this presentation, we will report our recent computational study on photo-induced hole injection rate at the interface between the metal halide perovskite (PVK) and organic hole transport materials (HTM). In this study, we use the density functional theory (DFT) for geometry optimization and excited state calculations. The rate constant is evaluated by using the Marcus theory in which several electronic excited states assigned to the local excitation in PVK are taken into account as initial state for the carrier injection process. The final state is assumed to be the lowest excited state assigned to a charge (electron) transfer state from HTM to PVK, corresponding to the hole injection from PVK to HTM. In evaluation of the electronic coupling matrix element, we apply by the generalized Mulliken-Hush model by Newton and Cave.

As HTMs, we herein focus on 4,4'-dimethoxy triphenylamine (DMeOTPA) which is a partial structure of spiro-OMeTAD (N2,N2,N2’,N2’,N7,N7,N7’,N7’-octakis(4-methoxyphenyl)-9,9’-spirobi[9H-fluorene]-2,2’,7,7’-tetramine). For comparison, we also study on 4,4'-dimethlthio triphenylamine (DMeSTPA) and 4,4'-dimethlseleno triphenylamine (DMeSeTPA). On the basis of the computational analysis, we will suggest a compound with higher efficiency in the photo-energy conversion, and will discuss important electronic properties of the materials in the interfacial hole transfer in PSC.