Near-Infrared Organic Photodetectors with Ultralow Dark Current for Photoplethysmogram Sensor and Optical...

Area of Science:

• Organic electronics
• Photodetector technology
• Materials science

Background:

• Suppressing dark current and noise is vital for highly sensitive organic photodetectors (OPDs).
• Existing challenges include controlling trap state density and interfacial charge injection, especially in near-infrared (NIR) OPDs.
• Various physical mechanisms contribute to dark current, such as shunt leakage and charge injection.

Purpose of the Study:

• To develop a strategy for reducing trap density and improving performance in NIR OPDs.
• To investigate the effect of a ternary blend on trap state density and device characteristics.
• To demonstrate the potential of these improved OPDs in practical applications.

Main Methods:

• A ternary blend strategy was employed, incorporating N2200 polymer acceptor into a NIR OPD blend (PCE10 donor and COTIC-4F acceptor).
• The trap density was measured before and after the addition of N2200.
• Device performance metrics, including dark current density and specific detectivity, were evaluated.

Main Results:

• The addition of 17 wt % N2200 decreased trap density from 5.25 × 10^15 cm^-3 to 2.16 × 10^15 cm^-3.
• The optimized device exhibited an ultralow dark current density of 3.21 × 10^-10 A cm^-2 at -0.1 V.
• A high specific detectivity exceeding 10^13 Jones was achieved across a broad spectral range (300-1100 nm).

Conclusions:

• The ternary blend strategy effectively reduces trap density in NIR OPDs.
• This approach leads to significant improvements in device sensitivity and performance.
• The developed OPDs show promise for applications in photoplethysmogram sensing and optical communication.