title: Spiro-OMeTAD single crystals: Remarkably enhanced charge-carrier transport via mesoscale ordering.
abstract: We report the crystal structure and hole-transport mechanism in spiro-OMeTAD [2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene], the dominant hole-transporting material in perovskite and solid-state dye-sensitized solar cells. Despite spiro-OMeTAD's paramount role in such devices, its crystal structure was unknown because of highly disordered solution-processed films; the hole-transport pathways remained ill-defined and the charge carrier mobilities were low, posing a major bottleneck for advancing cell efficiencies. We devised an antisolvent crystallization strategy to grow single crystals of spiro-OMeTAD, which allowed us to experimentally elucidate its molecular packing and transport properties. Electronic structure calculations enabled us to map spiro-OMeTAD's intermolecular charge-hopping pathways. Promisingly, single-crystal mobilities were found to exceed their thin-film counterparts by three orders of magnitude. Our findings underscore mesoscale ordering as a key strategy to achieving breakthroughs in hole-transport material engineering of solar cells.
authors.affiliation: Solar and Photovoltaics Engineering Research Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Dong
authors.identifier: 0000-0003-2916-6357
authors.initials: D
authors.lastname: Shi
authors.affiliation: Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First Street No. 2, Beijing 100190, P. R. China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Qin
authors.affiliation: Solar and Photovoltaics Engineering Research Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Yuan
authors.identifier: 0000-0002-4958-6132
authors.initials: Y
authors.lastname: Li
authors.affiliation: Imaging and Characterization Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Yao
authors.initials: Y
authors.lastname: He
authors.affiliation: Solar and Photovoltaics Engineering Research Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhong
authors.affiliation: Solar and Photovoltaics Engineering Research Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Jun
authors.initials: J
authors.lastname: Pan
authors.affiliation: Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First Street No. 2, Beijing 100190, P. R. China.
authors.forename: Huanli
authors.initials: H
authors.lastname: Dong
authors.affiliation: Imaging and Characterization Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.affiliation: Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First Street No. 2, Beijing 100190, P. R. China.
authors.forename: Wenping
authors.initials: W
authors.lastname: Hu
authors.affiliation: Solar and Photovoltaics Engineering Research Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Brédas
authors.affiliation: Solar and Photovoltaics Engineering Research Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
authors.forename: Osman M
authors.initials: OM
authors.lastname: Bakr
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D003460:Crystallization; D003461:Crystallography; D011211:Electric Power Supplies; D015394:Molecular Structure; D010087:Oxides / Q000737:chemistry*; D012993:Solar Energy; D013472:Sunlight; D014025:Titanium / Q000737:chemistry*
chemical_list: D017610:Calcium Compounds; D010087:Oxides; C059910:perovskite; D014025:Titanium
keywords: Materials science; crystal structure; hole-transport material; perovskite; photovoltaics; solar cells; solid-state dye-sensitized solar cell; spiro-OMeTAD