Semitransparent Organic Photovoltaic Devices: Interface/Bulk Properties and Stability Issues.

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Organic photovoltaic (OPV) devices offer potential for buildings' integrated photovoltaics.
• Understanding morpho/structural properties and stability of OPV components is crucial for device longevity.
• Key components include PM6:Y6 photo-active layer, ZnO electron transporting layer (ETL), HTL-X hole transporting layer (HTL), and Ag nanowires (AgNWs) electrode.

Purpose of the Study:

• To investigate the morpho/structural properties and stability of semitransparent organic photovoltaic devices.
• To identify degradation pathways under light and temperature stress.
• To propose and validate an alternative device configuration for enhanced stability.

Main Methods:

• In situ Energy Dispersive X-ray Reflectometry (EDXR) and ex situ Atomic Force Microscopy (AFM).
• X-ray Diffraction (XRD) and micro-Raman spectroscopy.
• Investigated effects of light and temperature stress on device components and interfaces.

Main Results:

• Devices exhibit essential structural stability, but ZnO/PM6:Y6 interface roughness increases.
• Thermal stress in the dark does not induce degradation, indicating photo-induced degradation.
• Micro-Raman spectroscopy reveals photo-oxidation of the active material due to hygroscopic HTL-X under illumination and moisture.
• ZnO layer may play a photocatalytic role in degradation.

Conclusions:

• Photo-oxidation of the active layer is the primary degradation mechanism, exacerbated by hygroscopic HTL-X.
• Replacing HTL-X with inorganic Molybdenum Oxide (MoOx) creates a stable alternative configuration.
• MoOx prevents photo-oxidation of the PM6:Y6 active material, thus enhancing device longevity under light stress.