Interplay between Interfacial Structures and Device Performance in Organic Solar Cells: A Case Study with the Low...

Area of Science:

• Organic electronics
• Materials science
• Photovoltaics

Background:

• Understanding interfacial effects is crucial for improving organic photovoltaic (OPV) device efficiency.
• Charge carrier recombination at interfaces is a major loss mechanism in OPVs.

Purpose of the Study:

• To investigate the correlation between interfacial properties and device performance in OPVs.
• To elucidate the role of interlayers in mitigating charge recombination.

Main Methods:

• Transient photovoltage (TPV) and charge extraction (CE) measurements.
• Synchrotron radiation photoemission spectroscopy (SRPES).
• Analysis of PCDTBT/PC71BM based OPV devices with and without a calcium (Ca) interlayer.

Main Results:

• Devices with a Ca interlayer showed lower charge recombination compared to those with only an Al cathode.
• SRPES revealed a strong dipole moment at the Ca interlayer interface.
• The Ca interlayer facilitated electron extraction and improved hole transport away from the cathode.

Conclusions:

• The Ca interlayer beneficially reduces interfacial recombination losses in OPVs.
• Interfacial band structure modification by the Ca interlayer enhances device performance.
• These findings explain the higher efficiencies observed in OPVs with Ca interlayers.