Ternary donor-insulator-acceptor systems for polymer solar cells

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Bulk heterojunction (BHJ) solar cells require optimized morphology for efficient charge generation and transport.
• Poly(3-butylthiophene) (P3BT) is a common organic semiconductor donor, often blended with phenyl-C61-butyric acid methyl ester (PCBM) as an acceptor.
• Controlling the nanoscale morphology of the BHJ active layer is crucial for device performance.

Purpose of the Study:

• To synthesize and investigate block copolymers of P3BT and polystyrene (PS) for BHJ solar cells.
• To evaluate the impact of varying polystyrene block lengths on the morphology and performance of P3BT/PCBM blends.
• To understand how the block copolymer structure influences miscibility, nanostructure formation, and charge transport.

Main Methods:

• Synthesis of P3BT-b-PS block copolymers with controlled PS block lengths.
• Fabrication of bulk heterojunction photoactive layers by blending P3BT-b-PS with PCBM.
• Characterization of blend morphology, including miscibility and nanostructure formation.
• Device performance testing to determine power conversion efficiency (PCE).

Main Results:

• Block copolymers with appropriate PS block lengths significantly improved PCE by an order of magnitude compared to pure P3BT/PCBM blends.
• The incorporation of PS blocks markedly enhanced the miscibility of the active layer blends.
• P3BT-b-PS self-assembled into nanorods with a P3BT core and a PS shell, forming nanoscale tunneling barriers.

Conclusions:

• Polystyrene block length is a critical parameter for controlling the morphology and performance of P3BT/PCBM BHJ solar cells.
• The self-assembled nanostructure of P3BT-b-PS provides efficient charge carrier transport pathways.
• Block copolymer engineering offers a promising strategy for optimizing organic photovoltaic devices.