Morphology-Controlled High-Efficiency Small Molecule Organic Solar Cells without Additive Solvent Treatment

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Solvent additives are commonly used to control morphology in organic solar cells.
• Achieving high power-conversion efficiencies (PCEs) often relies on precise control over the bulk-heterojunction (BHJ) morphology.
• Eliminating solvent additives presents a challenge for morphology control and high performance.

Purpose of the Study:

• To develop a solvent-free method for controlling nano-morphology in small-molecule organic solar cells.
• To achieve high power-conversion efficiencies (PCEs) without the use of solvent additives like 1,8-diiodooctane (DIO).
• To investigate the impact of bulk-heterojunction (BHJ) thickness on device performance.

Main Methods:

• Fabrication of small-molecule organic solar cells with varying BHJ thicknesses (100-320 nm).
• Morphology control achieved by omitting solvent additives.
• Performance evaluation through power-conversion efficiency (PCE) measurements.
• Generalized Transfer Matrix Method (GTMM) analysis to understand optical effects of BHJ thickness.

Main Results:

• A maximum PCE of 7.22% was achieved with a BHJ thickness of 320 nm.
• The absence of solvent additives did not preclude high efficiency, indicating successful morphology control.
• GTMM analysis confirmed the influence of BHJ thickness on device performance.

Conclusions:

• High PCE organic solar cells can be fabricated without solvent additive treatments.
• Controlling BHJ nano-morphology through methods other than solvent additives is feasible.
• Optimizing BHJ thickness is a critical factor for achieving high performance in solvent-free organic solar cells.