Enhancing Binary Organic Solar Cell Performance by Manipulating Molecular J-aggregation to Broaden Absorption and...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) face efficiency limitations due to the trade-off between light absorption and voltage loss, primarily caused by non-radiative recombination.
• The energy gap law dictates that a smaller energy gap, beneficial for absorption, often leads to increased voltage loss.

Purpose of the Study:

• To develop a co-additive treatment strategy to simultaneously enhance light absorption and reduce non-radiative recombination in PM6:BTP-eC9 based OSCs.
• To investigate the synergistic effects of 4-bromochlorobenzene (BCB) and 1,8-diiodooctane (DIO) on molecular aggregation and morphology.

Main Methods:

• Utilizing a co-additive treatment with solid BCB and liquid DIO to modulate molecular aggregation in the active layer.
• Analyzing the impact of additives on molecular ordering, J-aggregation, and optical bandgap.
• Fabricating OSC devices and characterizing their photovoltaic performance, including power conversion efficiency (PCE), fill factor (FF), and short-circuit current density (JSC).

Main Results:

• The co-additive treatment optimized molecular aggregation, leading to broader light absorption and reduced non-radiative recombination.
• OSCs achieved a PCE of 19.72% with a high FF of 81.3% and JSC of 28.61 mA cm⁻².
• Application of an anti-reflective MgF₂ layer further boosted JSC to 29.62 mA cm⁻² and PCE to 20.34%.

Conclusions:

• The BCB and DIO co-treatment effectively enhances molecular ordering and charge dynamics in OSCs.
• This strategy provides a practical approach to overcome efficiency limitations in organic photovoltaics.
• Achieved high performance metrics demonstrate the potential of this method for advancing OSC technology.