Super-durable closed-surface antireflection thin film by silica nanocomposites

- Closed-surface porous AR thin film was made via single dipping process.
- Closed-surface Silica AR sol was prepared with hollow nano-sphere and modified acid catalyzed processing.
- AR thin film preserves good AR capability and up to 2.5% short circuit current enhancement was achieved.
- Robust mechanical properties with 5 H pencil hardness was achieved.
- Only approximately 1% degradation after damp heat 2000 h.

A closed-surface silica antireflection thin film was prepared in single dipping process by growing branched silica chain from modified acid catalyzed sol-gel in hollow silica sphere sol-gel. The refractive index and thickness of thin film could be fine-tuned via acid catalyzed sol-gel content and withdrawing speed. Transmittance of this closed-surface AR thin film was as high as 97.1% with refractive index around 1.25-1.27. 2.5% gain in short circuit current was measured from both external quantum efficiency and flashing test on mini photovoltaic modules. The closed-surface structure was with a 5 H pencil hardness, and approximately 2.0 GPa indent hardness in nanoindenter test. It was resistant to high moisture and high temperature, mainly due to absence of voids on surface. The closed-surface AR thin film had potential to be applied in photovoltaic module, architecture windows in severe climate conditions.