Engineering the Core Units of Small-Molecule Acceptors to Enhance the Performance of Organic Photovoltaics

Hao Cheng Wang, Chung Hao Chen, Ren Hao Li, Yu Che Lin, Cheng Si Tsao, Bin Chang, Shaun Tan, Yang Yang, Kung-Hwa Wei*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Understanding the chemical structures of next-generation small molecules is a critical step for increasing the performance of organic photovoltaics (OPVs); an OPV's small molecule determines not only the extent of light absorption but also the morphology. Herein, four small molecules featuring different cores—indaceno dithiophene, dithienoindeno indaceno dithiophene (IDTT), substituted IDTT, and dithienothiophene-pyrrolobenzothiadiazole—denoted as ID-4Cl, IT-4Cl, m-ITIC-OR-4Cl, and Y7, respectively, are selected to form active layers with poly(quinoxaline) (PTQ10) and poly(benzodithiophene-4,8-dione) (PM6). The Y7 devices exhibit the best performance in both systems, with the power conversion efficiency (PCE) reaching 14.5%; in comparison, ID-4Cl device gives a PCE of 10.0% for blending with PTQ10 and a relative efficiency enhancement of 45%. The same trend occurs for the cases of PM6 blend devices. This enhancement is attributed to i) the improved short-circuit current density that is provided by the greater degree of conjugation in S, N-heteroarenes ladder-type fused-ring cores of Y7, ii) an induced face-on Y7 orientation and smaller domain sizes that result from the sp2-hybridized nitrogen side chain, and iii) smaller energy loss. This study reveals the importance of the core structure on the device performance and provides guidelines for the design of new materials for OPV technologies.

Original languageEnglish
JournalSolar RRL
StateE-pub ahead of print - Aug 2020


  • core units
  • grazing-incidence X-ray scattering
  • morphologies
  • organic solar cells
  • small-molecule acceptors

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