| Device configuration |
ITO/HTL/active layer/ETL/low-work-function metal (Al, Ca) cathode |
ITO (modified cathode)/ETL/active layer/HTL/high-work-function metal (Ag, Au) |
| Charge extraction |
Holes collected at bottom; electrons at the top electrode |
Electrons collected at bottom; holes at the top electrode |
| Electrode stability |
Reactive cathode prone to oxidation and corrosion |
Air-stable top electrode enhances durability |
| Sensitivity to oxygen/moisture |
Highly sensitive; faster degradation in ambient air |
Improved resistance to oxygen and moisture ingress |
| Interfacial stability |
PEDOT : PSS can etch ITO and induce instability |
Metal-oxide ETLs (ZnO, SnO2, and TiO2) provide robust interfaces |
| Thermal and operational stability |
Moderate stability: interfacial reactions accelerate aging |
Superior thermal and operational stability |
| Fabrication compatibility |
Often requires vacuum deposition of reactive metals |
Compatible with solution processing and scalable fabrication |
| Suitability for flexible devices |
Limited due to electrode reactivity |
Highly suitable for flexible and large-area devices |
| Overall stability outlook |
Lower long-term stability |
Preferred architecture for high-stability OSCs |
