TY - JOUR
T1 - New 3‐ethynylaryl coumarin‐based dyes for dssc applications
T2 - Synthesis, spectroscopic properties, and theoretical calculations
AU - Sarrato, João
AU - Pinto, Ana Lucia
AU - Malta, Gabriela
AU - Röck, Eva H.
AU - Pina, João
AU - Lima, João Carlos
AU - Parola, A. Jorge
AU - Branco, Paula Sério
N1 - PTDC/QUI‐QOR/7450/2020
POCI‐01‐0145‐FEDER‐016387
UIDB/50006/2020
UIDP/50006/2020
RECI/BBB‐BQB/0230/2012
RECI/BBB‐BEP/0124/2012
2020.09047.BD
PD/BD/135087/2017
PD/BD/145324/2019/ (G.M.)
.
PY - 2021/5/14
Y1 - 2021/5/14
N2 - A set of 3‐ethynylaryl coumarin dyes with mono, bithiophenes and the fused variant, thieno [3,2‐b] thiophene, as well as an alkylated benzotriazole unit were prepared and tested for dye‐sensitized solar cells (DSSCs). For comparison purposes, the variation of the substitution pattern at the coumarin unit was analyzed with the natural product 6,7‐dihydroxycoumarin (Esculetin) as well as 5,7‐dihydroxycomarin in the case of the bithiophene dye. Crucial steps for extension of the conjugated system involved Sonogashira reaction yielding highly fluorescent molecules. Spectroscopic characterization showed that the extension of conjugation via the alkynyl bridge resulted in a strong red‐shift of absorption and emission spectra (in solution) of approximately 73–79 nm and 52–89 nm, respectively, relative to 6,7‐dimethoxy‐4‐methylcoumarin (λabs = 341 nm and λem = 410 nm). Theoretical density functional theory (DFT) calculations show that the Lowest Unoccupied Molecular Orbital (LUMO) is mostly centered in the cyanoacrylic anchor unit, corroborating the high intramolecular charge transfer (ICT) character of the electronic transition. Photovoltaic performance evaluation reveals that the thieno [3,2‐b] thiophene unit present in dye 8 leads to the best sensitizer of the set, with a conversion efficiency (η = 2.00%), best VOC (367 mV) and second best Jsc (9.28 mA∙cm−2), surpassed only by dye 9b (Jsc = 10.19 mA∙cm−2). This high photocurrent value can be attributed to increased donor ability of the 5,7‐dimethoxy unit when compared to the 6,7 equivalent (9b).
AB - A set of 3‐ethynylaryl coumarin dyes with mono, bithiophenes and the fused variant, thieno [3,2‐b] thiophene, as well as an alkylated benzotriazole unit were prepared and tested for dye‐sensitized solar cells (DSSCs). For comparison purposes, the variation of the substitution pattern at the coumarin unit was analyzed with the natural product 6,7‐dihydroxycoumarin (Esculetin) as well as 5,7‐dihydroxycomarin in the case of the bithiophene dye. Crucial steps for extension of the conjugated system involved Sonogashira reaction yielding highly fluorescent molecules. Spectroscopic characterization showed that the extension of conjugation via the alkynyl bridge resulted in a strong red‐shift of absorption and emission spectra (in solution) of approximately 73–79 nm and 52–89 nm, respectively, relative to 6,7‐dimethoxy‐4‐methylcoumarin (λabs = 341 nm and λem = 410 nm). Theoretical density functional theory (DFT) calculations show that the Lowest Unoccupied Molecular Orbital (LUMO) is mostly centered in the cyanoacrylic anchor unit, corroborating the high intramolecular charge transfer (ICT) character of the electronic transition. Photovoltaic performance evaluation reveals that the thieno [3,2‐b] thiophene unit present in dye 8 leads to the best sensitizer of the set, with a conversion efficiency (η = 2.00%), best VOC (367 mV) and second best Jsc (9.28 mA∙cm−2), surpassed only by dye 9b (Jsc = 10.19 mA∙cm−2). This high photocurrent value can be attributed to increased donor ability of the 5,7‐dimethoxy unit when compared to the 6,7 equivalent (9b).
KW - Charge transfer
KW - Coumarin dyes
KW - Dye‐sensitized solar cells
KW - Ethynylaryl
KW - Thieno [3,2‐b] thiophene
UR - http://www.scopus.com/inward/record.url?scp=85106610061&partnerID=8YFLogxK
U2 - 10.3390/molecules26102934
DO - 10.3390/molecules26102934
M3 - Article
C2 - 34069210
AN - SCOPUS:85106610061
SN - 1420-3049
VL - 26
JO - Molecules
JF - Molecules
IS - 10
M1 - 2934
ER -