Funnel shaped molecules containing benzo/pyrido[1,2,5]thiadiazole functionalities as peripheral acceptors for organic photovoltaic applications (original) (raw)
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RSC Adv., 2014
We report a comparative study on four donor-acceptor benzothiadiazole-based copolymers containing dithienyl or thienothiophene moieties for application in organic photovoltaic (OPV) devices. Bulkheterojunction OPV devices are fabricated having power conversion efficiencies ranging between 4 and 6%. Morphological, spectroscopic and charge-transport measurements are used to investigate the influence of either the dithienyl or thienothiophene moieties on the structure and photophysical properties of the copolymer and copolymer:PC 71 BM blend films and rationalise the solar cell characteristics. Although all copolymer:PC 71 BM blends exhibit comparable hole polaron yields, solar cell devices with the highest power conversion efficiencies are correlated with increased charge-carrier mobility of the copolymer and enhanced aggregation of PC 71 BM in the blend. † Electronic supplementary information (ESI) available: OPV device optimisation data, GIWAXS measurements of pure polymer lms, AFM scans of blend lm surface, PL spectra of neat and blend thin-lms and OFET transfer and output characteristics. See
Chemistry of Materials, 2011
A new series of electron-deficient molecules based on a central benzothiadiazole moiety flanked with vinylimides has been synthesized via Heck chemistry and used in solution-processed organic photovoltaics (OPV). Two new compounds, 4,7bis(4-(N-hexyl-phthalimide)vinyl)benzo[c]1,2,5-thiadiazole (PI-BT) and 4,7-bis(4-(N-hexylnaphthalimide)vinyl)benzo[c]1,2,5-thiadiazole (NI-BT), show significantly different behaviors in bulk heterojunction (BHJ) solar cells using poly(3-hexylthiophene) (P3HT) as the electron donor. Two-dimensional grazing incidence X-ray scattering (2D GIXS) experiments demonstrate that PI-BT shows significant crystallization in spin-coated thin films, whereas NI-BT does not. Density functional theory (DFT) calculations predict that while PI-BT maintains a planar structure in the ground state, steric interactions cause a twist in the NI-BT molecule, likely preventing significant crystallization. In BHJ solar cells with P3HT as donor, PI-BT devices achieved a large open-circuit voltage of 0.96 V and a maximum device powerconversion efficiency of 2.54%, whereas NI-BT containing devices only achieved 0.1% power-conversion efficiency.
2020
In this paper, wepresent new organics chemical structures of pendant phenyl ester-substituted thiophene and benzothiadiazole based copolymers leading to donor (D)-acceptor (A) structure-types. Geometrics and photo-physical properties of the studied chemical structure are exploited in the further ground and excited-state. Theoretically, using the DFT and TD-DFT quantum chemical calculation implanted in Gaussian09 software, geometrical and electronic parameters such as the energy of HOMO and LUMO level, the Egap= EHomo- E Lumo and focused electronic parameters of the molecules were determined. It is obvious that the studied molecules show good photovoltaic properties. Thus, studied chemical structures are blended with acceptor compounds such as fullerene and PCBM derivatives in bulk-heterojunction solar cell. Quantic chemical calculations show that the studied compound present good electronic, optical and photovoltaic properties and can be used as potential electron donors in organic ...
Journal of Photonics for Energy, 2015
Two π-conjugated acceptor-donor-acceptor-donor-acceptor-type (A-D-A-D-A) oligothiophenes, TT-ð2T-DCV-HexÞ 2 and BT-ð2T-DCV-HexÞ 2 were designed and synthesized with thienothiadiazole (TT) or benzothiadiazole (BT) as the core and dicyanovinyl (DCV) as the terminal acceptor groups for comprehensively investigating and understanding structure-property relationships. The resulting oligomers were first characterized by thermal analysis, UV-Vis spectroscopy, and cyclic voltammetry. By simply changing the BT to TT core in these two oligothiophenes, the highest occupied molecular orbital levels were varied from −5.55 eV for BT-ð2T-DCV-HexÞ 2 to −5.11 eV for TT-ð2T-DCV-HexÞ 2 , and the optical band gaps were varied from 1.72 eV for BT-ð2T-DCV-HexÞ 2 to 1.25 eV for TT-ð2T-DCV-HexÞ 2 , ascribed to the stronger electron accepting character of the TT core. However, the power conversion efficiency of bulk heterojunction organic solar cells (OSCs) with TT-ð2T-DCV-HexÞ 2 as donor and [6,6]phenyl C 70 -butyric acid methyl ester (PC 71 BM) as acceptor was measured to be 0.04% only, which is much lower than that of BT-ð2T-DCV-HexÞ 2 ∶PC 71 BM (1.54%). Compared to the TT-ð2T-DCV-HexÞ 2 system, the BT-ð2T-DCV-HexÞ 2 based device shows smoother film surface morphology, and superior charge generation and charge carrier mobilities. Therefore, the results clearly demonstrate that in addition to modifying the alkyl side chains and π-bridge lengths, the design of new small molecules for high-performance OSCs should also aim to choose suitable acceptor units.
Journal of Polymer Science Part A: Polymer Chemistry, 2010
Two conjugated main-chain polymers consisting of heteroarene-fused p-conjuagted donor moiety alternating with 4,7-bis(5-bromo-4-octylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (P1) or 2,5-bis(5-bromo-4-octylthiophen-2-yl) thiazolo[5,4-d]thiazole (P2) units have been synthesized. They are intrinsically amorphous in nature and do not exhibit crystalline melting temperatures during thermal analysis. The effect of the fused rings on the thermal, optical, electrochemical, charge transport, and photovoltaic properties of these polymers has been investigated. The polymer (P1) containing 4,7-bis(5-bromo-4-octylthiophen-2yl)benzo[c][1,2,5] thiadiazole has a broad absorption extending from 300 to 600 nm with optical bandgaps as low as 2.02 eV. The HOMO levels (5.42 to 5.29 eV) are more sensitive to the choice of acceptor. The polymers were employed to fabricate organic photovoltaic cells with methanofullerene [6,6]-phenyl C71-butyric acid methyl ester (PC 71 BM). As a result, the polymer solar cell device containing P1 had the best preliminary results with an open-circuit voltage of 0.61 V, a short-circuit current density of 6.19 mA/cm 2 , and a fill factor of 0.32, offering an overall power conversion efficiency of 1.21%.
Beilstein journal of organic chemistry, 2017
A series of low band gap, planar conjugated polymers, P1 (PFDTBT), P2 (PFDTDFBT) and P3 (PFDTTBT), based on fluorene and benzothiadiazole, was synthesized. The effect of fluorine substitution and fused aromatic spacers on the optoelectronic and photovoltaic performance was studied. The polymer, derived from dithienylated benzothiodiazole and fluorene, P1, exhibited a highest occupied molecular orbital (HOMO) energy level at -5.48 eV. Density functional theory (DFT) studies as well as experimental measurements suggested that upon substitution of the acceptor with fluorine, both the HOMO and lowest unoccupied molecular orbital (LUMO) energy levels of the resulting polymer, P2, were lowered, leading to a higher open circuit voltage and short circuit current with an overall improvement of more than 110% for the photovoltaic devices. Moreover, a decrease in the torsion angle between the units was also observed for the fluorinated polymer P2 due to the enhanced electrostatic interaction b...
— Solution processed small molecules have drawn attention from the researcher and give competitive alternative to the polymer counterpart due to their advantages such as well define molecular structure and high purity without batch to batch variation. By incorporating D-A concept for structural framework, the photovoltaic performance of the small molecules had a great progress in recent years. The development of thieno[2,3-c]pyrrole-4,6-dione (TPD) as building block for small molecule Donor-Acceptor (D-A) structural framework had many potential advantages. This feature article reviews summarizes the progress of TPD based small molecules in organic photovoltaic cells.