New Perylene Diimide Ink for Interlayer Formation in Air-Processed Conventional Organic Photovoltaic Devices

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Roll-to-roll coating of organic photovoltaics requires efficient cathode interlayers compatible with air processing and green solvents.
• Traditional metal oxide interlayers face limitations including annealing requirements and layer interactions.
• Perylene diimide materials show promise as tunable, air-coatable cathode interlayers, but their electron extraction mechanisms require further investigation.

Purpose of the Study:

• To investigate the efficacy of two N-annulated perylene diimide materials (PDIN-H and CN-PDIN-H) as cathode interlayers in air-processed organic photovoltaic devices.
• To optimize ink formulations for green solvent processing and uniform film formation using spin and slot-die coating.
• To elucidate the role of cesium carbonate in forming hybrid organic/metal salt interlayers and understand their impact on device performance.

Main Methods:

• Synthesis and characterization of N-annulated perylene diimide materials (PDIN-H, CN-PDIN-H).
• Formulation of processing inks using cesium carbonate in green solvents (1-propanol, ethyl acetate).
• Fabrication of organic photovoltaic devices with PM6:Y6 active layers using spin and slot-die coating for cathode interlayer deposition.
• Device performance characterization, including power conversion efficiency (PCE) measurements.

Main Results:

• Achieved power conversion efficiencies of 13.2% (spin-coated) and 13.1% (slot-die coated) using PDIN-H/CN-PDIN-H based hybrid interlayers.
• Demonstrated superior performance compared to devices using the conventional PFN-Br interlayer (ca. 12.8% PCE).
• Identified the cathode interlayers as semi-insulating, with performance enhancement attributed to beneficial interfacial effects and electron tunneling.

Conclusions:

• N-annulated perylene diimides, when processed with cesium carbonate, serve as effective cathode interlayers for air-processed organic photovoltaics.
• The developed hybrid organic/metal salt interlayers enable high PCEs using scalable, green solvent-based coating techniques.
• These findings represent a significant advancement for the fabrication of high-performance, large-area organic solar cell modules.