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Three novel donor-pi-bridge-donor (D-pi-D) hole-transporting materials (HTMs) featuring triazatruxene electron-donating units bridged by different 3,4-ethylenedioxythiophene (EDOT) pi-conjugated linkers have been synthesized, characterized, and implemented in mesoporous perovskite solar cells (PSCs). The optoelectronic properties of the new dumbbell-shaped derivatives (DTTXs) are highly influenced by the chemical structure of the EDOT-based linker. Red-shifted absorption and emission and a stronger donor ability were observed in passing fromDTTX-1toDTTX-2due to the extended pi-conjugation.DTTX-3featured an intramolecular charge transfer between the external triazatruxene units and the azomethine-EDOT central scaffold, resulting in a more pronounced redshift. The three new derivatives have been tested in combination with the state-of-the-art triple-cation perovskite (FAPbI(3))(0.87)(MAPbBr(3))(0.13)CsPbI3in standard mesoporous PSCs. Remarkable power conversion efficiencies of 17.48 % and 18.30 % were measured forDTTX-1andDTTX-2, respectively, close to that measured for the benchmarking HTM spiro-OMeTAD (18.92 %), under 100 mA cm(-2)AM 1.5G solar illumination. PSCs withDTTX-3reached a PCE value of 12.68 %, which is attributed to the poorer film formation in comparison toDTTX-1andDTTX-2. These PCE values are in perfect agreement with the conductivity and hole mobility values determined for the new compounds and spiro-OMeTAD. Steady-state photoluminescence further confirmed the potential ofDTTX-1andDTTX-2for hole-transport applications as an alternative to spiro-OMeTAD.
Christophe Ballif, Quentin Thomas Jeangros, Christian Michael Wolff, Daniel Anthony Jacobs, Kerem Artuk, Xin Yu Chin
Mohammad Khaja Nazeeruddin, Pascal Alexander Schouwink, Sanghyun Paek, Cristina Roldán Carmona, Albertus Adrian Sutanto, Hobeom Kim, Marius Franckevicius, Kun-Han Lin, Nikita Drigo, Muhammad Sohail