Aqueous processing of low-band-gap polymer solar cells using roll-to-roll methods

Area of Science:

• Materials Science
• Organic Electronics
• Renewable Energy

Background:

• Developing efficient and sustainable materials for polymer solar cells (PSCs) is crucial for advancing renewable energy technologies.
• Traditional PSC fabrication often relies on hazardous organic solvents, posing environmental and health concerns.
• Aqueous-based processing offers a greener alternative, but achieving high-performance devices from waterborne inks remains a challenge.

Purpose of the Study:

• To prepare aqueous nanoparticle dispersions of three low-band-gap polymers (P1, P2, P3) for polymer solar cell applications.
• To investigate the film-forming properties and device performance of these aqueous inks using scalable coating techniques.
• To demonstrate the feasibility of environmentally friendly, roll-to-roll (R2R) fabrication of PSCs using water-based processing.

Main Methods:

• Aqueous nanoparticle dispersions were synthesized using ultrasonic treatment of polymer/fullerene ([60]PCBM) solutions with sodium dodecyl sulphate (SDS).
• Nanoparticle size was characterized by small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), grazing incidence SAXS (GISAXS), and grazing incidence wide-angle X-ray scattering (GIWAXS).
• High-quality films were fabricated via slot-die coating using aqueous dispersions with the nonionic detergent FSO-100, followed by R2R printing of all device layers.

Main Results:

• Stable aqueous dispersions of P1, P2, and P3 were successfully prepared and characterized.
• Slot-die coating enabled the formation of uniform films with controlled thicknesses (126 ± 19 nm for P1, 500 ± 25 nm for P2, 612 ± 22 nm for P3).
• Large-area inverted polymer solar cells fabricated using R2R slot-die and screen printing achieved power conversion efficiencies (PCEs) of 0.07% (P1), 0.55% (P2), and 0.15% (P3).

Conclusions:

• Aqueous nanoparticle dispersions of low-band-gap polymers can be effectively utilized for fabricating polymer solar cells.
• The developed water-based processing methods, including R2R slot-die and screen printing, are compatible with large-area device production.
• This work demonstrates a significant step towards sustainable and environmentally friendly manufacturing of organic photovoltaic devices.