Cleaving Fused-Ring Conjugated Structure and Introducing Aggregation-Induced Emission Effect Enable over 20%...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Enhancing photoluminescence quantum yield (PLQY) is crucial for reducing energy loss and increasing organic solar cell (OSC) performance.
• Aggregation-induced emission (AIE) offers a promising route to boost PLQY, but reliable molecular design strategies are lacking.
• Developing nonfullerene acceptors (NFAs) with controlled aggregation behavior is key for efficient OSCs.

Purpose of the Study:

• To design and synthesize a novel NFA with aggregation-induced emission (AIE) properties for improved OSC performance.
• To investigate the correlation between AIE characteristics, molecular aggregation, and energy loss in OSCs.
• To establish a molecular design strategy for high-performance NFAs in organic solar cells.

Main Methods:

• Molecular design and synthesis: Cleavage of the conjugated structure of AQ-fNI to create AQ-NI, an AIE-active NFA.
• Photophysical characterization: Measurement of PLQY for AQ-NI and AQ-fNI to assess emission enhancement.
• Device fabrication and characterization: Fabrication of binary (D18/AQ-NI) and ternary (D18:L8-BO:AQ-NI) OSCs using layer-by-layer (LBL) and bulk-heterojunction methods.
• Performance evaluation: Measurement of open-circuit voltage (V_OC), power conversion efficiency (PCE), and analysis of morphology and charge transport.

Main Results:

• The novel NFA, AQ-NI, exhibits a significantly higher PLQY (14.6%) compared to its precursor AQ-fNI (6.16%), indicating effective AIE.
• AQ-NI enables exceptionally low energy loss (0.494 eV) and a high V_OC (0.960 V) due to enhanced PLQY.
• The tailored aggregation behavior of AQ-NI promotes favorable phase separation and improved charge transport in the active layer.
• Binary OSCs based on D18/AQ-NI achieved a high PCE of 19.14%.
• Ternary OSCs (D18:L8-BO:AQ-NI) demonstrated an improved PCE of 20.22%, outperforming binary devices (19.39%).

Conclusions:

• A simple and effective molecular design strategy for high-performance NFAs with AIE properties has been established.
• The developed AIE-active NFA (AQ-NI) significantly enhances OSC performance by reducing energy loss and improving V_OC and PCE.
• This study highlights the fundamental link between AIE properties, molecular aggregation, and the efficiency of organic solar cells.