Refined Shockley-Queisser Framework-Guided Acceptor Design Enables Loss-Aware Bandgap Targeting in Organic Solar...

Area of Science:

• Materials Science
• Photovoltaics
• Organic Electronics

Background:

• Precise bandgap tuning is essential for maximizing power conversion efficiencies (PCEs) in organic solar cells (OSCs).
• The standard Shockley-Queisser (SQ) model provides an ideal limit but doesn't account for specific loss mechanisms in advanced OSCs.

Purpose of the Study:

• To refine the Shockley-Queisser model by including sub-bandgap absorption and nonradiative losses to predict an optimal optical bandgap for Y-series acceptor-based OSCs.
• To design and synthesize a novel acceptor material (YCF3-BO) to achieve this refined optimal bandgap.
• To investigate the performance of organic solar cells incorporating the new acceptor and explore their application in solar hydrogen production.

Main Methods:

• Modification of the Shockley-Queisser model to incorporate sub-bandgap absorption and nonradiative recombination.
• Design and synthesis of a new organic acceptor molecule (YCF3-BO) featuring CF3-terminated core and branched side chains.
• Fabrication and characterization of binary and ternary organic solar cell devices using PM6:YCF3-BO.
• Evaluation of device performance, including power conversion efficiency (PCE) and photoluminescence quantum yield (PLQY).
• Testing of PM6:YCF3-BO based photocathodes for underwater solar hydrogen production.

Main Results:

• A loss-aware optimal optical bandgap of approximately 1.41 eV was predicted for Y-series acceptor-based OSCs, exceeding the ideal SQ value.
• The synthesized YCF3-BO acceptor, when paired with PM6, yielded binary and ternary devices with PCEs of 19.8% and 20.2%, respectively.
• Improved PCEs were attributed to tuning the bandgap into the optimal window, enhancing PLQY, suppressing nonradiative recombination, and promoting 3D charge transport via branched side chains.
• Efficient operation of PM6:YCF3-BO photocathodes in underwater solar hydrogen production was demonstrated.

Conclusions:

• The study establishes a unified framework for advancing organic photovoltaics by integrating loss-aware bandgap theory with molecular design and solid-state packing control.
• The developed YCF3-BO acceptor and optimized device architecture significantly enhance PCEs in organic solar cells.
• The findings highlight the potential of these advanced organic solar cells for renewable energy applications, including solar hydrogen generation.