Bandgap Narrowing in Non‐Fullerene Acceptors: Single Atom Substitution Leads to High Optoelectronic Response Beyond 1000 nm
Abstract
Two narrow bandgap non‐fullerene acceptors (NBG‐NFAs), namely, COTIC‐4F and SiOTIC‐4F, are designed and synthesized for the fabrication of efficient near‐infrared organic solar cells (OSCs). The chemical structures of the NBG‐NFAs contain a D′‐D‐D′ electron‐rich internal core based on a cyclopentadithiophene (or dithienosilole) (D) and alkoxythienyl (D′) core, end‐capped with the highly electron‐deficient unit 2‐(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene)malononitrile (A), ultimately providing a A‐D′‐D‐D′‐A molecular configuration that enhances the intramolecular charge transfer characteristics of the excited states. One can thereby reduce the optical bandgap (Egopt) to as low as ≈1.10 eV, one of the smallest values for NFAs reported to date. In bulk‐heterojunction (BHJ) OSCs, NBG‐NFA blends with the polymer donor PTB7‐Th yield power conversion efficiencies (PCE) of up to 9.0%, which is particularly high when compared against a range of NBG BHJ blends. Most significantly, it is found that, despite the small energy loss (Egopt − eVOC) of 0.52 eV, the PTB7‐Th/NBG‐NFA bulk heterojunction blends can yield short‐circuit current densities of up to 22.8 mA cm−2, suggesting that the design and application of NBG‐NFA materials have substantial potential to further improve the PCE of OSCs.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 28, 2018
- Source ID
- 10.1002/aenm.201801212
Entities
People
- Akchheta Karki
- Benjamin R. Luginbuhl
- Guillermo C. Bazan
- Hansol Lee
- Jaewon Lee
- Katie Rosenthal
- Kilwon Cho
- Martin Seifrid
- Michael J Ford
- Seo‐Jin Ko
- Thuc‐quyen Nguyen
Organizations
- Office of Naval Research
- Office of Science
- Pohang University of Science and Technology
- United States Department of Energy
- University of California, Santa Barbara