Small-Molecule Donor/Polymer Acceptor-Based Organic Solar Cells Achieve >10% Efficiency

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Small-molecule donor/polymer acceptor (SD/PA) systems offer morphological stability in organic solar cells (OSCs).
• Excessive aggregation of small-molecule donors (SDs) in SD/PA systems hinders exciton dissociation and charge transport, limiting device efficiency.
• Optimizing morphology is crucial for enhancing the performance of SD/PA-based OSCs.

Purpose of the Study:

• To investigate the impact of a combined reverse thermal annealing and conventional thermal annealing (RTA&TA) post-treatment on the morphology of BTR-Cl/PY-IT-based SD/PA-OSCs.
• To elucidate how RTA&TA treatment influences SD aggregation and film morphology.
• To correlate morphological changes with improvements in device performance.

Main Methods:

• Implementation of a novel RTA&TA post-treatment strategy for SD/PA-OSC fabrication.
• Morphological characterization to analyze domain size and aggregation.
• Device performance testing to evaluate power conversion efficiency (PCE) and fill factor (FF).

Main Results:

• RTA&TA treatment effectively suppressed SD aggregation, reducing domain size from 73.92 nm to 52.80 nm.
• Morphological refinement led to enhanced exciton dissociation efficiency and accelerated charge transfer.
• Recombination losses were suppressed, resulting in a significant increase in PCE to over 10% and FF from 49.49% to 55.69%.

Conclusions:

• The RTA&TA post-treatment is a highly effective strategy for optimizing the morphology of SD/PA-based OSCs.
• This approach successfully mitigates SD aggregation issues, leading to substantial performance enhancements.
• RTA&TA offers a promising pathway for developing high-performance organic solar cells.