Case Snapshot

The Challenge​

Resolved local charge-transport behavior in operating organic electrochemical transistors

The Breakthrough​

Implemented electrochemical strain wave microscopy on Park NX10 with PinPoint imaging and lock-in detection

The Outcome​

Mapping local carrier transport and revealing microscopic defects that alter charge flow

Why It Matters​

Connecting nanoscale structure with functional transport behavior in operating OECT devices​

Visualizing Charge Transport in Organic Electrochemical Transistors

University of Bologna implemented electrochemical strain wave (ESW) microscopy on Park NX10 to map local charge transport in operating OECTs and reveal microscopic transport defects below the diffraction limit.

  • Customer: University of Bologna, Department of Physics and Astronomy, Italy
  • Research Focus: Organic Electrochemical Transistors / Charge Transport Characterization
  • Solution: Park NX10
  • Key Value: Mapping local charge transport and revealing microscopic transport defects

The Challenge

Organic electrochemical transistors (OECTs) rely on coupled ionic and electronic transport but understanding how charge moves locally through their mixed-conducting channels remains challenging. Conventional electrical measurements provide device-level information but cannot directly reveal microscopic variations in transport or identify local defects that disrupt charge flow.

“Understanding charge transport in OECTs required us to look beyond macroscopic electrical measurements and investigate how transport processes vary locally across the device channel. We needed an approach capable of connecting microscopic structure with functional transport behavior under operating conditions.”

— Tobias Cramer, Department of Physics and Astronomy, University of Bologna

The Solution

Park NX10 provided the AFM platform for implementing electrochemical strain wave microscopy, combining PinPoint imaging with electrochemical control and external lock-in detection to map local transport processes in operating OECT channels.

  • PinPoint-Based Multichannel Imaging: Acquired multichannel images of OECT channels using Park NX10 in PinPoint mode.
  • Electrochemical Strain Wave Detection: Applied modulated electrical excitation to detect strain waves associated with coupled charge transport and swelling in the OMIEC channel.
  • Amplitude and Phase Mapping: Used lock-in detection to map local swelling amplitude and phase through the NX10 auxiliary input channels.
  • In-Operando Transport Characterization: Mapped strain-wave propagation across n-type and p-type OECTs to investigate local transport behavior.

The Results

ESW microscopy revealed how local charge transport varies across operating OECT channels. Quantitative measurements captured carrier-concentration-dependent mobility behavior in both n-type and p-type devices, while comparison with AFM topography identified microscopic defects associated with local transport bottlenecks. The approach enabled transport properties to be mapped below the diffraction limit and linked device microstructure with functional behavior.

“Park NX10 provided the flexibility needed to implement electrochemical strain wave microscopy and investigate local transport processes in operating OECTs. This allowed us to connect microscopic device structure with functional charge-transport behavior.”

— Tobias Cramer

Key Outcomes

  • Mapped local electrochemical strain-wave amplitude and phase in operating OECT channels
  • Determined carrier-concentration-dependent mobility behavior in n-type and p-type devices
  • Revealed microscopic defects associated with local charge-transport bottlenecks
  • Connected OECT microstructure with functional transport behavior below the diffraction limit

Related Publication

This capability is further demonstrated through peer-reviewed research from the University of Bologna on electrochemical strain wave microscopy for investigating charge transport in organic electrochemical transistors, published in Small. (DOI: 10.1002/smll.202510345)