Organic solar cells using CVD-grown graphene electrodes.

Area of Science:

• Materials Science
• Organic Electronics
• Nanotechnology

Background:

• Flexible organic solar cells (OSCs) require efficient transparent conducting electrodes.
• Graphene synthesized via chemical vapor deposition (CVD) is a promising electrode material.
• Poor film formation of PEDOT:PSS on hydrophobic graphene hinders OSC fabrication.

Purpose of the Study:

• To develop a method for uniform PEDOT:PSS film coating on graphene electrodes for OSCs.
• To investigate the impact of multi-layer graphene anodes on OSC performance.
• To optimize graphene layer configuration for maximum power conversion efficiency (PCE).

Main Methods:

• Synthesis of graphene sheets using chemical vapor deposition (CVD).
• Development of a modified PEDOT:PSS solution ('GraHEL') with perfluorinated ionomers (PFI).
• Spin coating of 'GraHEL' onto multi-layer graphene electrodes on PET substrates.
• Fabrication and performance testing of flexible OSCs with varying graphene layer numbers.

Main Results:

• Uniform PEDOT:PSS films were successfully coated on graphene using the 'GraHEL' solution.
• Increasing graphene layers improved fill factor (FF) due to lower sheet resistance.
• Increasing graphene layers decreased short-circuit current (Jsc) due to reduced light absorption.
• Three-layer graphene (3LG) offered the optimal balance for power conversion efficiency (PCE).

Conclusions:

• The 'GraHEL' solution enables uniform PEDOT:PSS coating on CVD-graphene for flexible OSCs.
• Three-layer graphene (3LG) anodes provide the best performance trade-off for OSCs.
• Achieved a record PCE of 4.33% for OSCs utilizing CVD-graphene electrodes.