P3HT-based visible-light organic photodetectors using PEI/PAA multilayers as a p-type buffer layer

Area of Science:

• Organic electronics
• Photodetector technology
• Materials science

Background:

• Low leakage current is crucial for high-performance organic photodetectors (OPDs).
• Buffer layers are a key strategy to mitigate reverse-biased leakage current in OPDs.
• Polyelectrolyte multilayers offer potential as effective buffer layers.

Purpose of the Study:

• To investigate the integration of polyethyleneimine (PEI) and polyacrylic acid (PAA) polyelectrolyte multilayers as a p-type buffer layer in OPDs.
• To evaluate the impact of PEI/PAA buffer layers on leakage current, photocurrent, and overall device performance.
• To confirm the operating mechanism and assess the potential applications of the developed OPDs.

Main Methods:

• Spin-assisted layer-by-layer assembly was used to create PEI/PAA multilayers.
• Organic photodetectors with the configuration ITO/(PEI/PAA)2/P3HT:PC60BM/Yb/Al were fabricated.
• Device performance was characterized through current-voltage measurements, external quantum efficiency, transient photocurrent, and impedance analysis.

Main Results:

• The PEI/PAA buffer layers effectively suppressed leakage current while enhancing photocurrent via light-assisted tunneling.
• The optimized OPD with a (PEI/PAA)2 buffer layer achieved a specific detectivity of 3.11 × 10^12 Jones and a bandwidth of 103.2 kHz.
• The low-temperature solution process enables fabrication on flexible and large-area substrates.

Conclusions:

• PEI/PAA polyelectrolyte multilayers are effective p-type buffer layers for improving OPD performance.
• The developed OPDs demonstrate high detectivity suitable for applications like line scan cameras.
• The fabrication method allows for scalable production of flexible and large-area organic photodetectors.