Solvent Vapor Conditioning of Polymer-Polymer Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• All-polymer organic solar cells (OSCs) offer promising renewable energy solutions.
• Process optimization of donor-acceptor heterostructures remains a key challenge for OSCs.
• Current processing methods limit the stability and efficiency of polymer-based solar cells.

Purpose of the Study:

• To investigate the impact of hot mixing and solvent vapor conditioning (SVC) on the performance and stability of all-polymer OSCs.
• To understand how SVC affects the morphology and optoelectronic properties of the polymer active layer.
• To develop a scalable and cost-effective method for improving OSC power conversion efficiency (PCE).

Main Methods:

• Utilized the PM6:PYIT donor-acceptor system for all-polymer OSC fabrication.
• Employed hot mixing of polymer solutions to extend pot life.
• Applied systematic solvent vapor conditioning (SVC) at controlled activity ratios (0.01-0.1).
• Characterized solar cell performance (PCE, VOC, JSC, FF, shunt resistance) and film morphology (Vis-NIR spectroscopy).

Main Results:

• Hot mixing extended the pot life of polymer solutions from 10 minutes to over 15 hours without compromising PCE.
• SVC with specific solvent vapors (e.g., chloroform at activity 0.1) significantly improved PCE (from 13.2% to 14.7%) and shunt resistance (from 4 to 24 kΩ cm²).
• SVC optimized polymer packing and conformational order, leading to enhanced optoelectronic properties and suppressed dark leakage current.
• Exposure to saturated solvent vapor degraded cell performance.

Conclusions:

• Hot mixing and SVC are effective strategies for enhancing the processability and performance of all-polymer OSCs.
• SVC offers a scalable and inexpensive route to boost OSC efficiency and stability.
• The findings highlight the critical role of residual solvent vapors in OSC manufacturing and performance.
• Improved shunt resistance via SVC is beneficial for indoor photovoltaic applications under low-light conditions.