Heteroatom Effect on Star‐Shaped Hole‐Transporting Materials for Perovskite Solar Cells

• Published in: Advanced functional materials Vol. 28; no. 31
• Main Authors: García‐Benito, Inés, Zimmermann, Iwan, Urieta‐Mora, Javier, Aragó, Juan, Calbo, Joaquín, Perles, Josefina, Serrano, Alvaro, Molina‐Ontoria, Agustín, Ortí, Enrique, Martín, Nazario, Nazeeruddin, Mohammad Khaja
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01-08-2018
• Subjects: benzotriselenophene; Chalcogenides; Crystallography; Energy conversion efficiency; heteroatom effect; hole transporting materials; Materials science; Molecular orbitals; perovskite; Perovskites; Photovoltaic cells; Solar cells; Toluene; Transportation; Valence band
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201801734

Three new star‐shaped hole‐transporting materials (HTMs) incorporating benzotripyrrole, benzotrifuran, and benzotriselenophene central cores endowed with three‐armed triphenylamine moieties (BTP‐1, BTF‐1, and BTSe‐1, respectively) are designed, synthesized, and implemented in perovskite solar cells (PSCs). The impact that the heteroatom‐containing central scaffold has on the electrochemical and photophysical properties, as well as on the photovoltaic performance, is systematically investigated and compared with their sulfur‐rich analogue (BTT‐3). The new HTMs exhibit suitable highest‐occupied molecular orbitals (HOMO) levels regarding the valence band of the perovskite, which ensure efficient hole extraction at the perovskite/HTM interface. The molecular structures of BTF‐1, BTT‐3, and BTSe‐1 are fully elucidated by single‐crystal X‐ray crystallography as toluene solvates. The optimized (FAPbI3)0.85(MAPbBr3)0.15‐based perovskite solar cells employing the tailor‐made, chalcogenide‐based HTMs exhibit remarkable power conversion efficiencies up to 18.5%, which are comparable to the devices based on the benchmark spiro‐OMeTAD. PSCs with BTP‐1 exhibit a more limited power conversion efficiency of 15.5%, with noticeable hysteresis. This systematic study indicates that chalcogenide‐based derivatives are promising HTM candidates to compete efficiently with spiro‐OMeTAD.
A systematic study of the effect that heteroatom‐containing central scaffold (N, O, or Se) wields on the photovoltaic efficiency is investigated and compared with their sulfur analogue. The new star‐shaped derivatives endowed with three‐armed triphenylamine moieties show C
3 symmetry and a remarkable performance. This work highlights that chalcogenide‐based derivatives are promising hole‐transporting material candidates to compete efficiently with spiro‐OMeTAD.