Polymer solar cells with ternary blend nanolayers

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Polymer solar cells (PSCs) offer a promising alternative to conventional silicon-based photovoltaics due to their flexibility and low manufacturing costs.
• The power conversion efficiency (PCE) of PSCs is highly dependent on the morphology and properties of the active layer, typically a blend of electron-donating and electron-accepting polymers.

Purpose of the Study:

• To investigate the impact of solvent choice and film thickness on the performance of polymer solar cells utilizing a ternary blend.
• To understand the relationship between blend morphology, optical absorption, and device characteristics.

Main Methods:

• Fabrication of polymer solar cells using a blend of two electron-donating polymers (regioregular poly(3-hexylthiophene) (P3HT) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV)) and one electron-accepting polymer (poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT)).
• Systematic variation of solvent (p-xylene vs. chlorobenzene) and active layer film thickness.
• Characterization of device performance, including power conversion efficiency, and analysis of blend film morphology.

Main Results:

• Device performance was significantly improved when p-xylene was used as the solvent compared to chlorobenzene.
• Thicker blend films generally led to enhanced power conversion efficiency.
• A nanohole morphology observed in chlorobenzene-processed films, despite higher absorption, correlated with poorer device performance.

Conclusions:

• Solvent selection critically influences the morphology and performance of ternary polymer solar cells.
• Optimizing film thickness and controlling nanomorphology are crucial for enhancing PCE.
• Charge blocking resistances within the bulk polymer nanolayer represent a key limitation to achieving higher efficiencies in the current device architecture.