Laser-patterned functionalized CVD-graphene as highly transparent conductive electrodes for polymer solar cells

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Indium tin oxide (ITO) is a standard transparent conductive electrode in organic photovoltaic devices.
• ITO faces challenges including brittleness, high cost, and indium scarcity.
• Graphene offers a promising alternative due to its conductivity, transparency, and mechanical flexibility.

Purpose of the Study:

• To develop and optimize five-layer (5L) graphene as a transparent conductive electrode for inverted Polymer Solar Cells (PSCs).
• To address key challenges of low sheet resistance, high transparency, and surface wettability in graphene electrodes.
• To demonstrate scalable fabrication and assess the performance of graphene-based PSCs.

Main Methods:

• Fabrication of five-layer (5L) graphene on a glass substrate.
• Functionalization of graphene via p-doping (achieving 25 Ω□⁻¹) and O₂-plasma oxidation (achieving 134 Ω□⁻¹, 58° contact angle).
• Nd:YVO₄ laser patterning for scalable graphene electrode fabrication.
• Fabrication of inverted PSCs using PEDOT:PSS and ortho-xylene solvent for the active layer.

Main Results:

• Two distinct graphene functionalization methods were successfully applied.
• Laser patterning enabled scalable fabrication of graphene electrodes.
• Graphene-based inverted PSCs achieved a power conversion efficiency of 4.2%.
• This efficiency was demonstrated on the largest reported active area (10 mm²) for graphene-based inverted PSCs.

Conclusions:

• Functionalized five-layer graphene is a viable transparent conductive electrode for organic photovoltaic devices.
• The developed methods offer scalable and efficient routes for graphene electrode fabrication.
• Graphene-based PSCs show competitive performance, paving the way for ITO replacement.