Donor‐Acceptor Oligomers and Polymers Composed of Benzothiadiazole and 3‐Hexylthiophene: Effect of Chain Length and Regioregularity

Abstract

A series of donor-acceptor oligomer OBTTh n (n＝1-7) and polymer PBTTh 1 and PBTTh 2 composed of alternative 2,1,3-benzothiadiazole and 3-hexylthiophene have been designed and synthesized for the purpose of investigation on the effect of chain length and side-chain regioregularity on their basic properties and photovoltaic performance. In the OBTTh n oligomers and PBTTh 1 polymer, all the hexyl side chains on thienyl units orient toward the same direction. Upon elongation of the chain length, the intramolecular charge transfer (ICT) absorption band in solution gradually redshifts from 398 nm for OBTTh 1 to 505 nm for OBTTh 7 , then to 512 nm for PBTTh 1 polymer. Meanwhile, the HOMO energy level increases from −5.45 eV (OBTTh 1 ) to −5.08 eV (OBTTh 7 ) and −5.09 eV (PBTTh 1 ), and the LUMO energy level decreases from −3.11 eV (OBTTh 1 ) to −3.30 eV (OBTTh 7 ) and −3.33 eV (PBTTh 1 ), thus giving a smaller and smaller energy bandgap for higher oligomers and polymers. Theoretical calculation suggests straight line-like backbone geometry for this series of oligomers and polymer. On the other hand, polymer PBTTh 2 possesses a different side-chain regioregularity, in which every two neighbor hexyl side chains are arranged in different orienting direction. It is theoretically suggested to have curved line-like backbone geometry. In solution, it shows similar photophysical and electrochemical properties as PBTTh 1 . However in film state, it displays a less redshift in the ICT band as refer to that in solution than PBTTh 1 . In combination with [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM), these oligomers and polymers were used as donor material to fabricate organic bulk heterojunction solar cells. Again, chain length-dependent device photovoltaic performance was observed. The device based on OBTTh 4 showed a power conversion efficiency of 0.16%, while it increased to 0.36% and 0.49% for the devices based on OBTTh 6 and PBTTh 1 , respectively. However, the side-chain regioregularity has less influence on the device photovoltaic output since the device based on PBTTh 2 displayed an efficiency of 0.52%, comparable to that of PBTTh 1 .

One‐Pot Synthesis of 3‐ to 15‐Mer π‐Conjugated Discrete Oligomers with Widely Tunable Optical Properties

“…Monodisperse conjugated oligomers (MCOs) ( Đ = 1.0) with defined structures have been extensively studied to unravel the inherent chain‐length‐dependent properties for optoelectronic device applications. [ 2‐11 ] The π‐conjugated materials with high‐lying highest occupied molecular orbital (HOMO) containing exclusively electron‐donating (D) building blocks are a kind of ideal materials for hole transporting layers in organic electronic devices, such as organic light emitting diodes (OLEDs) [ 11‐14 ] and perovskite solar cells (PSCs), [ 15 ] etc . The previously reported all‐D long‐chain MCOs were mainly focused on ones that are made up of single electron‐ donating moieties, such as oligo‐phenylene, [ 16 ] ‐thiophene [ 17‐19 ] and ‐fluorene, [ 20 ] etc ., synthesized by Kumada, Suzuki or Stille C—M/C—Br (M = Mg, B and Sn) cross couplings.…”

Photovoltaic molecules based on vinylene-bridged oligothiophene applied for bulk-heterojunction organic solar cells

“…Monomers 7 and 8 were synthesized from Monomers 1 and 2 through Vilsmeier reaction, Wittig reaction and palladiumcatalyzed Heck reaction according to the refs. [28][29][30] . Finally, monomer 7 and monomer 8 reacted with 1,3-indanedione through Knoevenagal condensation reaction to obtain HEX-3TVT-ID and EH-3TVT-ID, respectively.…”

Benzodithiophene-Cored Small Optoelectronic Molecules: Influence of Extension Direction of Conjugated Segments

“…三种化合物的合成路线如 Scheme 1 所示, 其中中 间体 1 [19] , 2 [20] , 6 [21] , 7 [20] , 12 [19] 和苯并 [1,2-b:4,5-b']二噻 吩-4,8-二酮 [6a] 参照文献合成得到. 另一重要的中间体: …”