Interface-Engineered Organic Near-Infrared Photodetector for Imaging Applications

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Organic photodetectors (OPDs) are crucial for near-infrared (NIR) imaging.
• Achieving low dark current and high speed in OPDs remains a challenge.
• Understanding dark current mechanisms is key to device optimization.

Purpose of the Study:

• To develop a high-speed, low dark current NIR organic photodetector (OPD).
• To elucidate the dominant dark current mechanism in the OPD.
• To demonstrate the potential of the improved OPD in imaging applications.

Main Methods:

• Fabrication of OPDs on silicon substrates using amorphous indium gallium zinc oxide (a-IGZO) as the electron transport layer (ETL).
• Characterization using temperature-dependent current-voltage measurements, Q-DLTS, transient photovoltage decay, and ultraviolet photoelectron spectroscopy.
• Introduction of an interfacial layer to mitigate dark current.

Main Results:

• Identified trap-assisted field-enhanced thermal emission (Poole-Frenkel emission) as the primary dark current mechanism.
• Achieved a significantly reduced dark current of 125 pA/cm² at -1 V reverse bias by introducing an interfacial layer.
• Obtained fast photo response times of 639 ns (rise) and 1497 ns (fall).

Conclusions:

• The developed interfacial layer effectively suppresses dark current in NIR OPDs.
• The high-speed, low dark current OPDs are suitable for advanced imaging systems.
• Integration with CMOS read-out circuits demonstrates practical applicability for high-quality imaging.