Synthesis and Photovoltaic Properties of 2D-Conjugated Polymers Based on Alkylthiothienyl-Substituted Benzodithiophene and Different Accepting Units

Abstract

Abstract:Two new low bandgap conjugated polymers, PBDTS-ID and PBDTS-DTNT, containing isoindigo (ID) and naphtho [1,2-c:5,6-c ]bis[1,2,5]thiadiazole (NT), respectively, as an electron-deficient unit and alkylthiothienyl-substituted benzodithiophene (BDTS) as an electron-rich unit, were designed and synthesized by palladium-catalyzed Stille polycondensation. Both polymers showed good thermal stability up to 330 • C and broad absorption ranging from 300 to 842 nm. Electrochemical measurement revealed that PBDTS-ID and PBDTS-DTNT exhibited relatively low-lying highest occupied molecular orbital energy levels at −5.40 and −5.24 eV, respectively. These features might be beneficial for obtaining reasonable high open-circuit voltage and high short-circuit current. Polymer solar cells (PSCs) were fabricated with an inverted structure of indium-tin oxide/poly(ethylenimine ethoxylate)/polymer:PC 71 BM/MoO 3 /Ag. As a preliminary result, the PSCs based on PBDTS-ID and PBDTS-DTNT exhibited moderate power conversion efficiencies of 2.70% and 2.71%, respectively.

Recent advances in the application of isoindigo derivatives in materials chemistry

“…To increase the degree of conjugation in the structure of polymeric isoindigo, an introduction of additional aromatic fragments either into the main monomeric chain (compounds of type 33) [48][49][50] or as a side substituent in a thiophene unit (compounds of type 34) [51][52][53] was proposed. Among a number of compounds 33, the best efficiency (5.29%) was shown by an OSC based on a mixture of PC 71 BM and polymer 33с containing a short n-butyl substituent at the isoindigo nitrogen atoms and the longest and most branched alkyl radical in the p-phenylene fragment (Scheme 18).…”

Non-fullerene acceptors with alkylthiothiophene side chains for efficient non-halogenated solvent processed indoor organic photovoltaics

“…37 In addition, when the carbon alkyl side chain is substituted with sulfur alkyl, the crystallinity is enhanced, resulting in improved overall light-absorption ability, current flow, and PCE. [38][39][40][41] Moreover, thioalkyl side chains are expected to increase the charge transport because sulfur atoms are more easily polarized than carbon atoms, which can increase the intermolecular interactions.…”

Boosting the Power Factor of Benzodithiophene Based Donor–Acceptor Copolymers/SWCNTs Composites through Doping

“…The incorporation of the two-dimensional conjugated side-chain to the polymer backbone was confirmed to improve the electrical conductivity of conjugated polymers [ 31 , 32 , 33 ], thus was widely used as the active layers in the organic-field effect transistors (OFETs) and organic solar cells (OSCs) [ 34 , 35 ]. Recently, we attempted to investigate the thermoelectric performance of BDT-based polymers with two-dimensional conjugated side-chains [ 36 ] and obtained good thermoelectric power factor of 101.3 μWm −1 K −2 , which is almost 100 times larger than that of the BDT–EDOT copolymers with one dimensional aliphatic side chain (0.9 μWm −1 K −2 ).…”