Vertically Phase Separated Photomultiplication Organic Photodetectors with p-n Heterojunction Type Ultrafast Dynamic...

Area of Science:

• Organic electronics
• Photodetector technology

Background:

• Photomultiplication (PM)-type organic photodetectors (OPDs) achieve high external quantum efficiency (EQE) but suffer from high dark current and slow dynamics.
• These limitations stem from the long lifetime of trapped electrons in homogeneous distributions (HD) of n-type dopants within p-type polymer hosts.

Purpose of the Study:

• To develop a novel PM-type OPD with ultrafast dynamic properties.
• To overcome the trade-off between high responsivity and fast response times in existing OPDs.

Main Methods:

• A vertical phase separation (VPS) strategy was employed, creating distinct regions of p-type polymer and n-type acceptor within the photoactive layer.
• This VPS strategy was applied to create new VPS PM-type OPDs.

Main Results:

• VPS PM-type OPDs exhibited a 3-orders-of-magnitude increase in -3 dB cut-off frequency (120 kHz) and over 200-fold faster response times (rising time = 4.8 µs, falling time = 8.3 µs) compared to HD PM-type OPDs.
• High EQE (1121%) and specific detectivity (2.53 × 10¹³ Jones at -10 V) were maintained.
• Demonstrated the coexistence of p-n heterojunction (p-n HJ) and PM modes in a single photoactive layer for the first time.

Conclusions:

• The VPS strategy effectively enhances the dynamic performance of PM-type OPDs without compromising static properties.
• This innovative approach paves the way for OPDs with superior static and dynamic characteristics.