Flexible Organic Photodetectors with Mechanically Robust Zinc Oxide Nanoparticle Thin Films

Huikyeong Byeon, Boyun Kim, Hyejee Hwang, Minji Kim, Hyeonjin Yoo, Hyebin Song, Seoung Ho Lee, Byoung Hoon Lee

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Zinc oxide nanoparticle (ZnO-NP) thin films have been intensively used as electron transport layers (ETLs) in organic optoelectronic devices, but their moderate mechanical flexibility hinders their application to flexible electronic devices. This study reveals that the multivalent interaction between ZnO-NPs and multicharged conjugated electrolytes, such as diphenylfluorene pyridinium bromide derivative (DFPBr-6), can significantly improve the mechanical flexibility of ZnO-NP thin films. Intermixing ZnO-NPs and DFPBr-6 facilitates the coordination between bromide anions (from the DFPBr-6) and zinc cations on ZnO-NP surfaces, forming Zn2+-Br- bonds. Different from a conventional electrolyte (e.g., KBr), DFPBr-6 with six pyridinium ionic side chains holds the Br--chelated ZnO-NPs adjacent to DFP+ through Zn2+-Br--N+ bonds. Consequently, ZnO-NP:DFPBr-6 thin films exhibit improved mechanical flexibility with a critical bending radius as low as 1.5 mm under tensile bending conditions. Flexible organic photodetectors with ZnO-NP:DFPBr-6 thin films as ETLs demonstrate reliable device performances with high R (0.34 A/W) and D* (3.03 × 1012 Jones) even after 1000 times repetitive bending at a bending radius of 4.0 mm, whereas devices with ZnO-NP and ZnO-NP:KBr ETLs yield >85% reduction in R and D* under the same bending condition.

Original languageEnglish
Pages (from-to)10926-10935
Number of pages10
JournalACS Applied Materials and Interfaces
Issue number8
StatePublished - 1 Mar 2023

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© 2023 American Chemical Society.


  • flexible electronics
  • multicharged conjugated electrolyte
  • multivalent interaction
  • organic photodetectors
  • zinc oxide nanoparticle


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