High-efficiency nonfullerene organic solar cells: critical factors that affect complex multi-length scale morphology and device performance

Long Ye, Wenchao Zhao, Sunsun Li, Subhrangsu Mukherjee, Joshua H. Carpenter, Omar Awartani, Xuechen Jiao, Jianhui Hou, Harald Ade

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238 Citations (Scopus)


Organic solar cells (OSCs) made of donor/acceptor bulk-heterojunction active layers have been of widespread interest in converting sunlight to electricity. Characterizing of the complex morphology at multiple length scales of polymer:nonfullerene small molecular acceptor (SMA) systems remains largely unexplored. Through detailed characterizations (hard/soft X-ray scattering) of the record-efficiency polymer:SMA system with a close analog, quantitative morphological parameters are related to the device performance parameters and fundamental morphology–performance relationships that explain why additive use and thermal annealing are needed for optimized performance are established. A linear correlation between the average purity variations at small length scale (≈10 nm) and photovoltaic device characteristics across all processing protocols is observed in ≈12%-efficiency polymer:SMA systems. In addition, molecular interactions as reflected by the estimated Flory–Huggins interaction parameters are used to provide context of the room temperature morphology results. Comparison with results from annealed devices suggests that the two SMA systems compared show upper and lower critical solution temperature behavior, respectively. The in-depth understanding of the complex multilength scale nonfullerene OSC morphology may guide the device optimization and new materials development and indicates that thermodynamic properties of materials systems should be studied in more detail to aid in designing optimized protocols efficiently.

Original languageEnglish
Article number1602000
Number of pages10
JournalAdvanced Energy Materials
Issue number7
Publication statusPublished - 5 Apr 2017
Externally publishedYes


  • coherence length
  • interaction parameters
  • nonfullerene acceptors
  • organic solar cells
  • purity

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