Dominant Face-On Oriented Perylene-Diimide Interlayers for High-Performance Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Electron transport in cathode interlayers is critical for high-performance organic solar cells (OSCs).
• Traditional perylene-diimide (PDI) based interlayers often rely on strong doping, which can limit performance and stability.
• Controlling molecular orientation offers a potential pathway to enhance charge transport.

Purpose of the Study:

• To develop a novel non-ionic perylene-diimide (PDI)-based cathode interlayer with controlled molecular orientation.
• To investigate the effect of preferential face-on orientation and restricted doping on electron transport properties.
• To improve the power conversion efficiency and stability of organic solar cells.

Main Methods:

• Incorporation of bulky 1-(2,5,8-trioxadec-10-yl)-1,2,3-triazole (TOT) side chains into brominated-PDIs (PDIBr) via click chemistry to create PDIBr-TOT.
• Analysis of molecular orientation (face-on vs. edge-on) and doping effects.
• Fabrication and characterization of OSCs using PDIBr-TOT as cathode interlayers.

Main Results:

• PDIBr-TOT interlayers exhibited a dominant face-on molecular orientation due to the TOT side chains.
• The new interlayers showed negligible doping effects, unlike traditional PDIBr-N.
• Higher electron mobility was achieved through efficient vertical charge transport channels facilitated by the face-on orientation.
• OSCs integrated with PDIBr-TOT achieved a remarkable power conversion efficiency of 19.52% and enhanced device stability.

Conclusions:

• Controlling face-on molecular orientation in non-ionic PDI-based cathode interlayers is an effective strategy to enhance electron transport and OSC performance.
• Restrained doping effects contribute to improved device stability.
• This approach offers a promising direction for designing advanced cathode interlayers for future organic solar cell development.