Scratch resistance and durability enhancement of bulk heterojunction organic photovoltaics using ultra-thin alumina layers

• Mechanical behavior of AlOx films deposited on glass and OPVs evaluated.
• Increased organic content of the AlOx encapsulant enhances OPV modulus and hardness.
• AlOx abrasive stress relief proceeds through surface cracking followed by film buckling.

Atomic layer deposition (ALD) was studied for ultra-thin (≤100 nm) barrier coating deposition onto organic photovoltaics (OPVs) to enhance device lifetime. Herein, we report the first known investigation of the mechanical characteristics of AlOx encapsulated OPVs using nanoindentation and scratch testing with deposition temperature as a tunable parameter. The higher organic content in the AlOx film, grown at lower temperatures, enhanced the interfacial bonding at the AlOx–OPV interface and provided modulus and hardness performance exceeding that of a common polymer encapsulant. Furthermore, AlOx׳s organic content impeded fracture propagation, confirming the durability enhancement associated with this approach.