Ultra high barriers based on cellulose nanofibrils

Purpose and goal

The main scientific objective was to develop foils of cellulose nanofibril material or CNF, a novel bio-based material into a material with exceptional water vapor barrier and optical performance for encapsulation of solar cells and OLEDs. A further technological objective was to develop a roll-to-roll process method for coating of CNF roll. The main challenge is in fact to produce a CNF foil in a continuous process due to the demanding drying operations to achieve moisture-free CNF.

Expected results and effects

The materials developed was in the form of multilayer films based on CNF substrates and inorganic and/or hybrid coatings. The demands for solar cells is 10-4 g/m2 d for water vapour transmission and for OLEDS 10-6 g/m2 d. Concerning solar cells, the target has probably been fulfilled using hybrid coated CNF with inorganic layer. When it comes to OLEDs, the use inorganic layers deposited on hybrid coated CNF foils has lead to a value of 10-5 g/m2 d revealed by the calcium test method, an improvement factor of 500. Fabrication of CNF rolls is now running in pilot scale.

Planned approach and implementation

Coating of CNF foils was partly performed with a laboratory roller coater after development of CNF rolls. This simulated an industrial scale fabrication of coating of CNF rolls. The coating of CNF consisted of a multilayer of organic and inorganic coating and the performance of these foils are now being tested in the same set-up as for pre-commercial foils to be used for solar cells.