Full Papers
doi.org/10.1002/cplu.202100208
ChemPlusChem
(3.71×10À 4 cm2 VÀ 1 sÀ 1), which also contributes to the modest Acknowledgements
performance of TPASe-1 and TPASe-2 PSC devices in compar-
ison with spiro-OMeTAD.
We thank the Swiss National Funds for Scientific Research contract
To shed light on the hole-extraction capability of the
selenophene-based HMTs compared to spiro-OMeTAD, steady-
state photoluminescence (PL) spectra were recorded (Fig-
ure 5d). Upon excitation, the pristine triple-cation perovskite
film shows a strong PL band centered at 785 nm, which is
clearly quenched when the HTMs are deposited on top of the
perovskite, indicating that the photogenerated holes are
efficiently extracted at the perovskite/HTM interface. However,
it should be noted that spiro-OMeTAD presents a significantly
more efficient hole-extraction behavior than the selenium-
containing HTMs, and among the later TPASe-1 performs better
than TPASe-2, which is in good agreement with the photo-
voltaic performance measured in PSCs.
number 200020 L 172929/1. The authors also thank the Spanish
Ministry of Science and Innovation (MICINN) (projects CTQ2017-
83531-R, PGC2018-099568-BÀ I00, RED2018-102815-T, Centro de
Excelencia Severo Ochoa SEV-2016-0686, and Unidad de Excelen-
cia María de Maeztu CEX2019-000919-M), the CAM (QUIMTRONIC-
CM project Y2018/NMT-4783), the Generalitat Valenciana (PROM-
ETEO/2020/07), and European Feder funds (PGC2018-099568-
BÀ I00). J.A. and A.M.O. are grateful to MICINN for “Ramon-y-Cajal”
fellowships (RyC-2017-23500, RYC2019-027280-I). L.I. thanks to the
Universidad del Valle (CIAM-2017) and the Science, Technology
and Innovation Fund-General Royalties System (FCTeI-SGR) under
contract BPIN 2013000100007 for a predoctoral fellowship. Borun
New Material Technology generously supplied the high-quality
spiro-OMeTAD.
Conclusion
Conflict of Interest
In summary, the design and synthesis of two new hole-
transporting materials, TPASe-1 and TPASe-2, using the 3,4-
dimethoxyselenophene unit as central scaffold have been
described. The new HTMs incorporate two p-meth-
oxytriphenylamine TPA donor units, linked through single and
triple bonds to the central spacer, and are prepared following
straightforward syntheses with relatively good yields. They
show highly conjugated, almost planar, donor-π-bridge-donor
structures. Both HTMs exhibit strong absorption and emission
in the visible region and adequate HOMO alignment (À 5.18 eV
and À 5.43 eV for TPASe-1 and TPASe-2, respectively) with the
The authors declare no conflict of interest.
Keywords: donor-bridge-donor systems
materials · perovskite solar cells · photophysics · selenophenes
· hole-transporting
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valence
band
edge
of
the
triple-cation
[(FAP-
bI3)0.87(MAPbBr3)0.13 0.92
]
[CsPbI3]0.08 perovskite (À 5.70 eV). The
donor-acceptor-donor linker group influences the electro-
chemical properties of the two new HTMs. The single bonds
promote the extraction of two consecutive electrons from the
donor TPA units in TPASe-1. In comparison, the triple bonds
induce the simultaneous extraction of two electrons from the
TPA units due to the enhanced conjugation in TPASe-2. The
selenium-based HTMs were applied in n-i-p mesoporous
perovskite solar cells using the state-of-the-art [(FAP-
bI3)0.87(MAPbBr3)0.13 0.92[CsPbI3]0.08 as light absorber, reaching
]
moderate efficiencies (13.72 and 12.44% for TPASe-1 and
TPASe-2, respectively), lower than those obtained for the
reference compound of spiro-OMeTAD (17.78%). The limited
performance of the selenium-based HTMs is attributed to the
poor film-formation ability of both derivatives on top of the
perovskite layer and also to their lower hole mobility in
comparison to spiro-OMeTAD. Both HTMs form layers contain-
ing pinholes, which have a clear negative impact on the
photovoltaic performance. Photoluminescence experiments
on perovskite/HTM thin films show that the hole-extraction
ability of the HTM decreases in passing from spiro-OMeTAD to
TPASe-1 and to TPASe-2, in good agreement with the
decrease observed in the PSC performance.
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ChemPlusChem 2021, 86, 1006–1013
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