Influence of Bridging Groups on the Photovoltaic Properties of Wide-Bandgap Poly(BDTT-alt-BDD)s

Abstract

To further advance polymer solar cells requires the fast evolution of π-conjugated materials as well as a better understanding of their structure−property relationships. Herein, we present three copolymers (PT1, PT2, PT3) made through tuning π-bridges (without any group, thiophene, and 3-hexylthieno [3,2-b]thiophene) between electron-rich (D: BDTT) and -deficient (A: BDD) units. The comparative studies reveal the unique correlation that the tune of π-bridge on the polymeric backbone governs the solid stacking and photovoltaic properties of resultant poly(BDTTalt-BDD)s, which provide an effective way to deliver new and efficient polymer with feasible processability. That is, polymers with either twist zigzag backbone (PT1) or with linear coplanar backbone (PT2) result in inferior photovoltaic performance upon simple solution casting. Among them, PT3 with extended zigzag backbone and planar segments exhibits suitable processability and retains good efficiency in nonfullerene solar cells through a single-solvent cast without involving tedious treatments. This work illustrates that the tuning of the D−π−A polymer backbone facilitates efficient materials with feasible processability, promising for scale-up fabrication.

Highly Efficient All-Polymer Solar Cells from a Dithieno[3,2-f:2′,3′-h]quinoxaline-Based Wide Band Gap Donor

“…Both polymers showed two maximum absorption peaks (λ max ) in the solution and film. The I 0–0 peaks are assigned to the intermolecular aggregation of the polymer donor, and the I 0–1 peaks originate from the strong intramolecular charge transfer (ICT) between electron rich (D) 4,8-bis­[5-(2-ethylhexyl)-4-fluorothiophen-2-yl]­benzo­[1,2-b:4,5-b′]­dithiophene section and the electron deficient (A) dithieno­[3,2- f :2′,3′- h ]­quinoxaline (BQx) part of the polymer donor (Figures c) . In the dilute CB solution, although PBQx-Me-TF and PBQx-H-TF polymers show absorptions in the range of 420–620 nm, the λ max peak of PBQx-H-TF exhibited a small redshift of 569 nm from that of PBQx-Me-TF whose peak is at 564 nm.…”

“…These results indicate that subtle molecular structure adjustment to make a polymer donor work cooperatively with the polymer acceptor allows for considerable progress and achieves a desirable PCE in all-PSCs. 44 In the dilute CB solution, although PBQx-Me-TF and PBQx-H-TF polymers show absorptions in the range of 420−620 nm, the λ max peak of PBQx-H-TF exhibited a small redshift of 569 nm from that of PBQx-Me-TF whose peak is at 564 nm. The redshift possibly originates from the stronger ICT effect of PBQx-H-TF over PBQx-Me-TF.…”

Benzodithiophenedione-based polymers: recent advances in organic photovoltaics

“…Chen et al designed a set of experiments to explore the relationship between photovoltaic properties and molecular conformation on the main backbone. Through tuning πbridges (without and with thiophene or 3-hexylthieno [3,2b]thiophene) between the BDT and BDD units, these polymers with different conformation tendencies for P72 (zigzag), P73 (linear), and P74 (zigzag) exhibited different aggregation states 60 . Since the alkyl side chains yielded a steric twist angle, P74 had a more twisted backbone than that of P73 and led to a change from linear to zigzag conformation.…”

Thiophene-Based Trimers and Their Bioapplications: An Overview

“…The benzodithiophenedione structure is another cyclic ketone and serves as acceptor unit in donor-acceptor copolymers for photovoltaic applications ( Scheme 17 , II). Trimers formed by a central benzodithiophenone linked to two thiophene rings are prepared by Stille coupling and present some variation on the pendant group [ 242 , 326 , 327 , 328 , 329 , 330 , 331 , 332 , 333 ]. Finally, a terthiophene linked to a non-cyclic β-diketone was also reported ( Scheme 17 , III) [ 334 ].…”