1,4-Di(3-alkoxy-2-thienyl)-2,5-difluorophenylene: A Building Block Enabling High-Performance Polymer Semiconductors with Increased Open-Circuit Voltages

Abstract

A new building block, 1,4-di(3-alkoxy-2thienyl)-2,5-difluorophenylene (DOTFP) with several desirable features such as high backbone planarity, suitably lying highest occupied molecular orbital (HOMO), and good solubility, was developed by inserting an electron-deficient difluorophenylene into the 3,3′-dialkoxy-2,2′-bithiophene (BTOR) unit. Three regioregular D-A 1 -D-A 2 type polymers based on DOTFP and benzothiadiazole (BT) derivatives were synthesized and characterized by comparing with a D−A type BTOR-based polymer. The content of highly electron-rich alkoxythiophene is reduced by half in the DOTFP-based polymers versus that of the BTOR-based polymer analogue, which results in a deeper HOMO level and benefits high open-circuit voltage (V oc ) in polymer solar cells (PSCs). Consequently, the DOTFP-ffBT-based solar cells exhibited a significantly improved power conversion efficiency (PCE) of 8.7% and an increased V oc of 0.84 V compared to the BTOR-ffBT-based solar cells with a PCE of 2.6% and a V oc of 0.49 V. Additionally, the DOTFP-based polymers showed improved charge transport properties and film morphology than the BTOR-based polymer BTOR-ffBT, resulting in simultaneous enhancement of the short-circuit current (J sc ) and fill factor (FF) in PSCs. These results demonstrate the great promise of the DOTFP building block for the construction of high-performance photovoltaic polymer semiconductors with increased V oc s.

Synthesis of π-Conjugated Polymers Containing Benzotriazole Units via Palladium-Catalyzed Direct C-H Cross-Coupling Polycondensation for OLEDs Applications

“…Hence, the LUMO energy levels of polymers P1 – P4 can be obtained to be −3.60, −3.68, −3.59, and −3.58 eV, respectively, versus Fc/Fc + according to the corresponding E onset red . Since the conjugated polymers containing fluorinated benzotriazole segments can display excellent oxidational stability due to the stabilized HOMO and LUMO levels by the strong inductive effect of fluorine atoms [ 11 , 42 ], such polymer materials should have a huge potential for application in various photoelectric devices.…”

Head-to-Head Linked Dialkylbifuran-Based Polymer Semiconductors for High-Performance Organic Thin-Film Transistors with Tunable Charge Carrier Polarity

“…Please note that the FMOs of these BFR-based polymers are considerably low lying compared to those of their polymers based on alkoxy chainsubstituted HH bithiophene. 39,51 Although the noncovalent sulfur•••oxygen interactions lock the polymer backbone to achieve a planar conformation, the strong electron-donating alkoxy chains lead to elevated HOMO levels. 39,46,51 Therefore, our strategy of using dialkylated bifuran shows a distinctive advantage, avoiding high-lying HOMO levels, which should yield improved materials and device stability in OTFTs.…”

“…39,51 Although the noncovalent sulfur•••oxygen interactions lock the polymer backbone to achieve a planar conformation, the strong electron-donating alkoxy chains lead to elevated HOMO levels. 39,46,51 Therefore, our strategy of using dialkylated bifuran shows a distinctive advantage, avoiding high-lying HOMO levels, which should yield improved materials and device stability in OTFTs. 52,53 The narrower E g opt s of the CNBFR-based polymers than the FBFR-based polymers are mainly attributed to their highly suppressed E LUMO s as a result of the strong electronwithdrawing cyano groups.…”

“…28,30,45 Moreover, the off-currents (I off s) of 10 −10 −10 −8 A and I on /I off s of 10 5 are much better than those of HH-linked bithiophene-containing analogous polymers with alkoxy side chains, which typically show high I off s of 10 −7 −10 −6 A and small I on /I off s of 10 2 −10 3 in transistors due to the highpositioned FMO energy levels. 46,51,60 The results reflect the advantages of the strategy of reducing steric hindrance by incorporating furan versus the strategy of employing noncovalent S•••O interaction by introducing a strong electrondonating alkoxy chain. Switching the acceptor monomer to cyano-functionalized benzothiadiazole DCNBT changed the charge carrier polarity to n-type for polymers CNBFR-C18 and CNBFR-BO, as a result of their deep-positioned LUMOs.…”

High‐Performance All‐Small‐Molecule Organic Solar Cells Enabled by Regio‐Isomerization of Noncovalently Conformational Locks

“…into the polymeric-organic semiconductors can enhance the rigidity of the backbone and reduce the internal reorganization energy, thus increasing charge transport mobility and device performance. [25][26][27][28][29][30][31] Furthermore, NoCLs usually can obviously reduce the synthetic steps in comparison to the strategy of covalently locking the neighboring aromatic rings. In particular, NoCLs have been employed to construct low-cost and high-performance nonfused-ring electron acceptors for OSCs, which exhibited exciting PCE over 15% and high figure-of-merit value.…”