Wide Bandgap Polymer Donor with Acrylate Side Chains for Non‐Fullerene Acceptor‐Based Organic Solar Cells

Abstract

Organic semiconductors inherently have a low dielectric constant and hence high exciton binding energy, which is largely responsible for the rather low power conversion efficiency of organic solar cells as well as the requirements to achieve delicate bulk-heterojunction nanophase separation in the active layer. In this study, methyl acrylate as a weakly electron-withdrawing side chain for the electron rich thiophene to prepare a new building block, methyl thiophene-3-acrylate (TA), with increased polarity is used. A wide bandgap polymer PBDT-TA synthesized using TA and a benzodithiophene (BDT) monomer shows increased dielectric constant and reduced exciton binding energy compared to the analogous polymer PBDT-TC, which is made of BDT and methyl thiophene-3-carboxylate (TC). An organic solar cell device based on PBDT-TA:ITIC also achieves a higher power conversion efficiency of 10.47% than that of the PBDT-TC:ITIC based solar cell (9.68%). This work demonstrates the effectiveness of using acrylate side chains to increase the dielectric constant, reduce the exciton binding energy, and enhance the solar cell efficiency of polymer semiconductors.

Acetal- and Aldehyde-Substituted Thiophene-Benzodithiophene Copolymers for Organic Solar Cells

“…Notably, di-BDTFT exhibits significantly lower HOMO and LUMO energy levels of −5.09 and −2.50 eV, respectively, compared to di-BDTTh with HOMO and LUMO energy levels of −4.88 and −2.11 eV. The HOMO/LUMO energy levels of di-BDTFT are also lower than those of the dimer model compound for PBDTTC, di-BDT-TC ( E HOMO / E LUMO = −4.99/–2.22 eV) . These results once again affirm that FT serves as a stronger electron-accepting building block than TC.…”

“…The HOMO/LUMO energy levels of di-BDTFT are also lower than those of the dimer model compound for PBDTTC, di-BDT-TC (E HOMO /E LUMO = −4.99/−2.22 eV). 22 These results once again affirm that FT serves as a stronger electron-accepting building block than TC. It is worth noting that the dihedral angle between the first BDT and FT units is 22.92°, larger than that between BDT and Th in di-BDTTh (9.62°) but slightly smaller than that between BDT and TC (24.8°).…”

“…3 To obtain relatively inexpensive, yet high-performing, D−A donor polymer materials, copolymerizing BDT with a synthetically easily accessible thiophene monomer that has an electron-withdrawing substituent is an effective approach. 14−16 In line with this, our group has developed several new thiophene building blocks with an electron-withdrawing substituent at the 3-position, such as TI, 17,18 TO, 19−21 and TA 22 (Figure 1). These monomers, synthesized from 3formylthiophene, serve as cost-effective precursors for polymers exhibiting promising solar cell performance.…”

“…Polymers consisting of alternating donor (D) and acceptor (A) building blocks are the most important class of donor materials for NFA-based OSCs since their energy levels and bandgaps are easily tunable. ,, Benzodithiophene (BDT) derivatives are the most widely used D units for high-performance donor polymers due to their planar structure, stability, and appropriate electron donating effect . To obtain relatively inexpensive, yet high-performing, D–A donor polymer materials, copolymerizing BDT with a synthetically easily accessible thiophene monomer that has an electron-withdrawing substituent is an effective approach. − In line with this, our group has developed several new thiophene building blocks with an electron-withdrawing substituent at the 3-position, such as TI, , TO, − and TA (Figure ). These monomers, synthesized from 3-formylthiophene, serve as cost-effective precursors for polymers exhibiting promising solar cell performance.…”

Benzodithiophene with multiple side-chains for efficient wide-bandgap D–A copolymers

“…5c and d) with smaller domain sizes, which is also beneficial for achieving higher J SC and FF values of the corresponding OSC. 42…”