Impact of Nonfullerene Molecular Architecture on Charge Generation, Transport, and Morphology in PTB7‐Th‐Based Organic Solar Cells
Abstract
Despite the rapid development of nonfullerene acceptors (NFAs), the fundamental understanding on the relationship between NFA molecular architecture, morphology, and device performance is still lacking. Herein, poly[[4,8‐bis[5‐(2‐ethylhexyl)thiophene‐2‐yl]benzo[1,2‐b:4,5‐b0]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]‐thieno[3,4‐b]thiophenediyl]] (PTB7‐Th) is used as the donor polymer to compare an NFA with a 3D architecture (SF‐PDI4) to a well‐studied NFA with a linear acceptor–donor–acceptor (A–D–A) architecture (ITIC). The data suggest that the NFA ITIC with a linear molecular structure shows a better device performance due to an increase in short‐circuit current ( Jsc) and fill factor (FF) compared to the 3D SF‐PDI4. The charge generation dynamics measured by femtosecond transient absorption spectroscopy (TAS) reveals that the exciton dissociation process in the PTB7‐Th:ITIC films is highly efficient. In addition, the PTB7‐Th:ITIC blend shows a higher electron mobility and lower energetic disorder compared to the PTB7‐Th:SF‐PDI4 blend, leading to higher values of Jsc and FF. The compositional sensitive resonant soft X‐ray scattering (R‐SoXS) results indicate that ITIC molecules form more pure domains with reduced domain spacing, resulting in more efficient charge transport compared with the SF‐PDI4 blend. It is proposed that both the molecular structure and the corresponding morphology of ITIC play a vital role for the good solar cell device performance.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 21, 2018
- Source ID
- 10.1002/adfm.201802702
Entities
People
- Bhoj Gautam
- Carr Hoi Yi Ho
- Chen Dong
- Erik Klump
- Franky So
- Harald Ade
- Iordania Constantinou
- John R. Reynolds
- Sai‐wing Tsang
- Seth Marder
- Xiaochu Ba
- Xueping Yi
- Yuanhang Cheng
- Zhengxing Peng
Organizations
- City University of Hong Kong
- Fayetteville State University
- Georgia Tech
- North Carolina State University
- Office of Naval Research
- United States Department of Energy