Photocurrent generation through electron-exciton interaction at the organic semiconductor donor/acceptor interface

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) rely on efficient charge generation at donor/acceptor interfaces.
• Understanding photocurrent generation mechanisms is crucial for improving OSC performance.

Purpose of the Study:

• To elucidate the role of electron-exciton interaction in photocurrent generation within organic solar cells (OSCs).
• To investigate the coexistence of electron-exciton interaction and exciton dissociation at the donor/acceptor interface.

Main Methods:

• Fabrication of indium tin oxide/copper phthalocyanine (CuPc)/fullerene (C60)/molybdenum oxide/Al heterojunction OSCs.
• Analysis of photocurrent generation mechanisms using transient photovoltage measurements.
• Evaluation of external quantum efficiency (EQE) to understand charge carrier dynamics.

Main Results:

• Electron-exciton interaction and exciton dissociation were found to coexist at the CuPc/C60 interface.
• A reverse photocurrent was observed due to charge extraction at opposite sides (electrons at CuPc, holes at C60).
• The primary photocurrent contribution originates from electron-exciton interaction, with exciton dissociation also playing a role.

Conclusions:

• Electron-exciton interaction is a significant contributor to photocurrent generation in specific OSC architectures.
• The findings provide insights into charge carrier dynamics at organic semiconductor interfaces.
• This research contributes to the fundamental understanding of photovoltaic mechanisms in organic solar cells.