Synthesis and characterization of low band gap random copolymers based on cyclopentadithiophene and thiophene carboxylates for photovoltaic applications

Abstract

We have synthesized a series of conjugated random copolymers-P1-COOR 0 , P2-COOR 00 , and P3-COOR 00 -containing electron-donating units based on (4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b 0 ]dithiophene), alkyl 3-thiophene carboxylate, and thiophene by Stille polycondensation method. The polymers were characterized by 1 H NMR spectroscopy, gel permeation chromatography (GPC), UV-Vis absorption spectroscopy, and cyclic voltammetry. The optical band gaps of the polymers varies from 1.88 to 1.93 eV and their absorption characteristics can be tuned by adjusting the ratio of the two electron-donating units: (4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b 0 ] dithiophene) and thiophene. These polymers exhibit broad and strong absorption between 300 and 700 nm with good solubility and thermal stability. Electrochemical studies indicate sufficiently deep HOMO levels and it gives high open-circuit voltage in the bulk heterojunction device when fullerene derivatives are used as electron acceptors. By changing the ratio of the two donor monomers, the highest occupied molecular orbital energy levels of polymers varies between -5.04 and -5.19 eV and the lowest unoccupied molecular orbital energy levels range from -3.16 to -3.26 eV. Preliminary results on solar cell fabrication using the synthesized polymers show open-circuit voltage in the range of 0.62-0.63 V.

Diversity-oriented synthesis of benzo[b]thiophenes fused to medium-sized N-heterocycles via Friedel–Crafts cyclization processes

“…9 Moreover, these multi-substituted and functionalized thiophene polycycles have also gained popularity in the area of polymer and material sciences. For instance, polythiophene conducting polymers are common components of electroluminescent devices, 10 transistors, 11 nanotubes 12 and optimal imaging devices. 13 Given the large array of synthetic utility, structural complexity and astonishing biological profile of condensed thiophenes, a flexible route to regioselective access to these significant condensed scaffolds from readily available acyclic precursors is an attractive goal.…”

Enhancing Polymer Photovoltaic Performance via Optimized Intramolecular Ester-Based Noncovalent Sulfur···Oxygen Interactions

“…We report here the design and synthesis of a new ester-substituted bithiophene building block, 3-alkoxycarbonyl-3′-alkoxy-2,2′-bithiophene (TETOR, Chart ), and the corres-ponding polymer semiconductors. To reduce the TRTOR electron-rich character, the electron-donating alkyl chain is replaced with an electron-withdrawing ester moiety, which downshifts the HOMOs, thereby increasing the PSC V oc s and improving OTFT air stability. ,− For instance, the ester-functionalized polythiophenes show downshifted HOMOs (∼− 5.10 eV vs −4.8 eV), which lead to improved V oc s (∼0.8 V vs 0.62 V) in PSCs in comparison with P3HT . To date, the low bandgap polymers PTB7 and PTB7-Th yield state-of-the-art photovoltaic performance, mainly due to the electron-withdrawing ester units, increasing the PSC V oc s to 0.76 and 0.84 V, respectively. ,,− Recently, an ester-functionalized PB3T polymer was reported to exhibit excellent photovoltaic performance in non-fullerene-based PSCs with PCE up to 11.9% .…”

Enhanced Electron Transfer Mediated by Conjugated Polyelectrolyte and Its Application to Washing-Free DNA Detection

“…To function as a redox label that allows a high signal-tobackground ratio, an ideal CPE should have (i) high redox and/ or electrocatalytic activity, (ii) high water solubility, (iii) long chain length (>10 nm), and (iv) low nonspecific adsorption. Figure 1a shows a p-type polymer backbone based on cyclopentadithiophene and thiophene (CDT_T) 10 that was employed to achieve facile electrochemical oxidation near 0 V vs Ag/AgCl. Anionic 4-sulfonatobutyl (SB) side chains were incorporated to obtain high water solubility 11 and low nonspecific adsorption.…”