Dendritic core carbazole-based hole transporting materials for perovskite solar cells: molecular design, photovoltaic performance and impact of hole transporters and doping on the electrical response of the photovoltaic devices
Thanh-Tuan Bui a, Maria Ulfa b, Federica Maschietto b, Alistar Ottochian b, Mai-Phuong Nghiêm a, Ilaria Ciofini b, Fabrice Goubard a, Thierry Pauporté b
a University of Cergy-Pontoise, Mail Gay Lussac, 5, Neuville-sur-Oise, France
b Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris (IRCP), 11 rue P. et M. Curie, F-75005 Paris, France.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Oral, Thanh-Tuan Bui, presentation 010
Publication date: 23rd October 2018

Designing organic molecules efficient for charge extraction and transport when integrated into optoelectronic devices remains a great challenge for many advanced applications. In perovskite solar cells (PSCs), the hole extraction/transport and the device stability are strongly dependent on the molecular structure of the hole transporting material (HTM). Herein we have engineered a dendritic core carbazole-based HTM, which combines the advantages of both small molecules and polymeric materials. We have investigated in-depth the relationship between the chemical structure of the HTM and both the photovoltaic efficiency and the device stability. The development of new HTMs alternative to Spiro-OMeTAD and the understanding of the role of doping agents on these layers are also important research axes in the field. It requires the use of appropriate characterization tools enabling to discriminate the bulk and interface effects. In the present work, we fully analyze the effect of HTM doping and of the material on the impedance response of PSCs. It has been shown that the dendritic core is a promising approach leading to both enhanced device performance and stability. The new HTM has been proved to act as a good barrier and protect satisfactorily the perovskite surface. The power conversion efficiencies (PCE) increase from 11.5% for the simple model compound to a promising 14.6%.Additionally, the normalized PCE of carbazole-based PSC decreased by only 5% after more than three weeks of storage under ambient conditions meanwhile the cell using the most popular HTM (Spiro-OMeTAD)dropped off by more than 40%. The presented results demonstrate that introducing dendritic concept is a simple strategy to design HTM for efficient and stable PSC (1). We also show that the impedance spectroscopy is of high practical interest for the development of new HTMs and for the optimization of the layer doping (2).

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