Self-Assembled Benzotriazole Interlayer Stabilizes ZnO/Polymer Interfaces Enables Thermally Robust Organic Solar...

Area of Science:

• Materials Science
• Renewable Energy Technologies
• Organic Electronics

Background:

• Improving the operational lifespan of organic solar cells (OSCs) is critical for their commercial viability.
• Thermal degradation pathways, including MoO3 diffusion and ZnO interactions, limit OSC device stability.
• Interfacial engineering offers a promising route to enhance OSC performance and longevity.

Purpose of the Study:

• To investigate the impact of a benzotriazole (BTA) molecular layer on the thermal stability of organic solar cells.
• To elucidate the mechanisms by which BTA modification improves interfacial properties and device performance.
• To provide a scalable strategy for enhancing OSC durability under thermal stress.

Main Methods:

• Spin-coating of a benzotriazole (BTA) molecular layer at the ZnO/active layer interface.
• Fabrication and thermal aging (85 °C for 1000 h) of BTA-modified and unmodified OSC devices.
• Characterization using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS).

Main Results:

• BTA modification significantly improved thermal stability, with devices retaining 86% of initial efficiency after 1000 h at 85 °C, versus 70% for control devices.
• BTA suppressed MoO3 diffusion and its detrimental interaction with ZnO, reducing energy level mismatch and recombination.
• XPS and UPS analysis indicated BTA reduced adsorbed oxygen on ZnO and lowered its work function, enhancing charge transport.

Conclusions:

• A solution-processable BTA interfacial layer effectively enhances the thermal stability of organic solar cells.
• BTA modification mitigates key degradation pathways, leading to improved long-term operational performance.
• This interfacial engineering approach offers a practical solution for developing more durable organic solar cell devices.