Improving the Thermal Stability of Inverted Organic Solar Cells by Mitigating the Undesired MoO₃ Diffusion toward...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) require improved thermal stability for commercialization.
• Thermal degradation mechanisms in OSCs hinder long-term performance.
• Understanding degradation pathways is key to developing stable OSCs.

Purpose of the Study:

• To investigate the thermal degradation mechanism in a specific OSC structure.
• To demonstrate a strategy for enhancing the thermal stability of OSCs.
• To elucidate the role of an interfacial layer in mitigating degradation.

Main Methods:

• Fabrication of structure-inverted OSCs with a TCTA interlayer.
• Thermal annealing at 150 °C to induce degradation.
• X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) for interface analysis.
• Drift-diffusion simulations to model degradation.

Main Results:

• Thermal annealing caused (MoO3)- formation and diffusion, leading to p-doping and performance loss (JSC, VOC, FF).
• A 4,4',4″-tris(carbazol-9-yl)-triphenylamine (TCTA) interlayer suppressed (MoO3)- diffusion.
• TCTA-interlayer cells maintained high performance (>16% PCE) after hot-press encapsulation and showed excellent stability at 85 °C.

Conclusions:

• The TCTA interlayer effectively prevents detrimental (MoO3)- diffusion, enhancing OSC thermal stability.
• The study provides a viable strategy for fabricating robust organic solar cells.
• The findings contribute to the commercialization prospects of OSC technology.