Conjugated Mesopolymer Achieving 15% Efficiency Single-Junction Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• High molecular weight polymers used in organic solar cells (OSCs) present challenges like low solubility and synthetic difficulty, leading to batch variations.
• Conjugated mesopolymers, with molar masses between 1-10 kDa, offer a potential solution to these issues.

Purpose of the Study:

• To design and synthesize a novel mesopolymer donor material for OSCs.
• To investigate the impact of molecular weight on the performance and batch consistency of benzo[1,2-b:4,5-b']difuran-based photovoltaic materials.

Main Methods:

• Synthesis of three donor materials: a novel mesopolymer (MePBDFClH), a lower molecular weight mesopolymer (MePBDFCL), and a high molecular weight polymer (PBDFCl).
• Fabrication and characterization of organic solar cells using these materials.
• Analysis of miscibility, phase separation, and power conversion efficiency (PCE).

Main Results:

• The MePBDFClH mesopolymer achieved a record power conversion efficiency (PCE) of 15.06% for benzo[1,2-b:4,5-b']difuran-based materials.
• MePBDFClH demonstrated appropriate miscibility and phase separation in blend films, contributing to its high performance.
• Mesopolymer MePBDFCL showed less than 5% PCE variation between batches, significantly reducing batch-to-batch differences compared to the polymer PBDFCl (12% decrease).

Conclusions:

• Mesopolymers are promising for developing high-performance organic photovoltaic materials with reduced batch-to-batch variation.
• The benzo[1,2-b:4,5-b']difuran unit is identified as a viable electron-donating core for OSC applications.