4.7 Article

Wide-Band Gap Small-Molecule Donors with Diester-Terthiophene Bridged Units for High-Efficiency All-Small-Molecule Organic Solar Cells

Journal

ACS APPLIED ENERGY MATERIALS
Volume 4, Issue 6, Pages 5868-5876

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acsaem.1c00683

Keywords

diester-terthiophene; benzodithiophene; small-molecule donors; non-fullerene acceptor; all-small-molecule organic solar cells

Funding

  1. National Natural Science Foundation of China [51673031, 51573154]
  2. Major Program of the Natural Science Research of Jiangsu Higher Education Institutions [20KJA480004]
  3. Top-notch Academic Programs Project of Jiangsu Higher Education Institutions (TAPP)
  4. Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
  5. Jiangsu Provincial Talents Project of High-Level Innovation and Entrepreneurship
  6. Research Innovation Program for Postgraduate of Jiangsu Province [KYCX19_1751]

Ask authors/readers for more resources

This study utilized diester-terthiophene as a pi-bridged unit to construct wide-band gap small-molecule donors, achieving ordered molecular stacking and deep E-HOMO levels. The BER6 and BECN molecules demonstrated high power conversion efficiency and a high V-OC in all-small-molecule OSCs.
It is crucial to maintain both an ordered intermolecular packing and deep highest occupied molecule orbital energy levels (E-HOMO) for cutting-edge organic solar cells (OSCs) with a high open-circuit voltage (V-OC). Although halogen substitution has become the most popular strategy to lower the E-HOMO of donor materials, there still remains great room for exploring new approaches to construct wide-band gap small-molecule donors (SMDs) with a deeper E-HOMO. For this purpose, in this work, we primarily took a strategy of diester-terthiophene as a pi-bridged unit to construct a type of wide-band gap SMDs named BER6 and BECN with an A-pi-D-pi-A framework using alkyl-thienyl-substituted benzo-dithiophene as a central electron-donating (D) unit and rhodanine or cyanoacetate derivatives as a terminal electron-accepting (A) unit. It is found that both molecules have almost coincident coplanarity and dipole interaction for the diester-terthiophene unit. As a result, an ordered molecular stacking and a deep E-HOMO of about -5.40 eV with an optical band gap of 1.85-1.91 eV are presented for both molecules. A high power conversion efficiency of 9.03% with a high V-OC of 0.97 eV was obtained in the BER6/IDIC-based all-small-molecule OSCs (ASM-OSCs). Our results demonstrate that diester-terthiophene is a promising strategy to develop wide-band gap SMDs applied in high-performance ASM-OSCs.

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