New highly-flexible and durable polyimide-integrated graphene electrodes

UNIST scientists have demonstrated a graphene-based electrode through direct integration of thermally stable polyimide (PI) on graphene, where PI serves a bifunctional role as a carrier film for graphene transfer and substrate for the graphene. 

These graphene-based electrodes enabled scientists to make organic solar cells (OSCs) that can achieve the highest power conversion efficiency (PCE). Moreover, it is promising for use in various optoelectronic devices requiring high efficiency and flexibility.

This approach yielded a thermally stable graphene electrode with a low sheet resistance of 83 Ω/sq enabled by a polymer residue-free graphene surface, as well as outstanding mechanical durability via improved adhesion between the graphene and PI substrate.

In addition to its optical transmittance over 92%, the proposed graphene-based OSCs exhibit outstanding mechanical robustness during up to 10,000 bending cycles along with a PCE of 15.2%, which is comparable to that of indium-tin-oxide-based reference device fabricated on a rigid glass substrate (15.7%).

Donghwan Koo (Combined M.S/Ph.D. of Energy and Chemical Engineering, UNIST), the first author of the study, said“Using the PI-assisted graphene electrode, flexible OSC with a PCE of 15.2% was obtained with outstanding mechanical robustness. Moreover, direct integration of PI improved the durability of the graphene electrode by inhibiting delamination of the graphene under mechanical stress.”

Schematic Describing the Two-Step Fabrication Process of PI@GR
Schematic Describing the Two-Step Fabrication Process of PI@GR

Professor Park said, “The proposed electrode is promising for use in various optoelectronic devices requiring high efficiency and flexibility. Thus, it is expected to be of great help in the development of various next-generation flexible photoelectric devices, such as high-performance LEDs and light sensors, as well as solar cells.”

Journal Reference:
  1. DonghwanKoo, SungwooJung, Flexible Organic Solar Cells Over 15% Efficiency with Polyimide-Integrated Graphene Electrodes. DOI: 10.1016/j.joule.2020.02.012

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