Saddle-like, π-conjugated, cyclooctatetrathiophene-based, hole-transporting material for perovskite solar cells

A flexible, saddle-like, π-conjugated skeleton composed of four fused thiophene rings forming a cyclooctatetrathiophene (CoTh) with four triphenylamines ( CoTh-TTPA ) is presented as a hole-transporting material (HTM) for perovskite solar cells. The new HTM shows a bright red color stemming from a d...

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Published in:Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2019-06, Vol.7 (22), p.6656-6663
Main Authors: Urieta-Mora, Javier, García-Benito, Inés, Zimmermann, Iwan, Aragó, Juan, Calbo, Joaquín, Grancini, Giulia, Molina-Ontoria, Agustín, Ortí, Enrique, Martín, Nazario, Nazeeruddin, Mohammad Khaja
Format: Article
Language:English
Subjects:
Charge transfer
Conjugation
Energy conversion efficiency
Molecular orbitals
Perovskites
Photoluminescence
Photovoltaic cells
Solar cells
Valence band
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Summary:A flexible, saddle-like, π-conjugated skeleton composed of four fused thiophene rings forming a cyclooctatetrathiophene (CoTh) with four triphenylamines ( CoTh-TTPA ) is presented as a hole-transporting material (HTM) for perovskite solar cells. The new HTM shows a bright red color stemming from a direct conjugation between the TPA groups and the central CoTh scaffold. This results in a charge transfer band due to the combination of the weak acceptor moiety, the CoTh unit, and the electron-donating p -methoxytriphenylamine groups. CoTh-TTPA exhibits a suitable highest-occupied molecular orbital (HOMO) level in relation to the valence band edge of the perovskite, which ensures efficient hole extraction at the perovskite/HTM interface. It has been applied as the HTM in combination with a mixed perovskite ([FAPbI 3 ] 0.85 [MAPbBr 3 ] 0.15 ) and a state-of-the-art triple cation perovskite ([(FAPbI 3 ) 0.87 (MAPbBr 3 ) 0.13 ] 0.92 [CsPbI 3 ] 0.08 ) reaching noticeable light-to-energy conversion efficiencies of 16.3 and 15.9%, respectively. These values are slightly lower than those measured for the benchmark spiro-OMeTAD HTM. The HTM properties have been analyzed by means of photoluminescence and conductivity experiments, which demonstrated a better hole extraction and conductivity for spiro-OMeTAD. A new HTM incorporating a saddle-like, thiophene-rich core endowed with four triphenylamine units is proposed. The new HTM leads to PSCs reaching efficiencies up to 16.3%.
ISSN:2050-7526
2050-7534
DOI:10.1039/c9tc00437h