Selective ultra-short-pulsed laser ablation for scribing of organic photovoltaics and decorative applications

Diverse coatings improve the functionality of abundant products and enable complex systems in the field of thin film electronics. Ultra-thin coatings can enhance the optical appearance of technical products. For technical and decorative effects these coatings need to be removed locally and selectively from the substrate in any desired one or two-dimensional shape without damaging the substrate surface or influencing the underneath layer functionalities. Alternating deposition and laser based structuring of functional layers allows fabrication of low cost and highly efficient organic photovoltaics (OPV) or flexible electronics e.g. for wearables. Short and ultrashort pulsed lasers allow a precise, fast and selective ablation of thin functional films with minimum or no damage to the subjacent layers and substrates. State of the art OPV systems consist of at least three merely 100 nm thin layers- a transparent electrode, an organic photoelectric stack and a top electrode. To ensure proper and long term operation of OPVs an external encapsulation by two ultra-barrier foils isolates the cells from environmental oxygen and water vapor. The advantage of this kind of encapsulation is faced by two major disadvantages: high costs (~1/3 of total manufacturing costs) and parasitic intrinsic water due to sponge effects of the OPV substrate foil. A promising approach to fight these drawbacks is to use the OPV substrate itself as barrier by enhancing its functionality through the integration of an ultra-barrier coating, followed by alternating deposition and laser structuring of OPV functional layers. In effect, more functionality will be integrated into less material and production steps are reduced in number. This promising approach introduces a new challenge: since the ultra-barrier now is integrated as 1st functional layer, no violation of the barrier functionality by the following process steps is allowed, while all electrical functionalities must be maintained. In this publication, results and investigations on laser processing of organic stack (P2) and top electrode (P3) are presented utilizing short and ultrashort pulsed laser systems with UV, VIS and IR wavelengths. Characterization of the processing results is realized by different techniques such as the optical Ca-test as the ""gold standard"" and Hyperspectral imaging (HSI) as a novel, fast and contact-free method. In addition, results of two-dimensional coating removal for decorative applications will be presented. Shaping of the spatial intensity profile widens the process window and prevents damage to the subjacent materials.

This publication presents the highly selective laser ablation of functional ~110EL250 nm layers of novel flexible organic photovoltaics (P2 and P3) as well as decorative coatings by short and ultra-short pulsed laser systems with UV, GR and IR wavelengths. Main focus is on the structuring without damaging the subjacent ultra-barrier layer and substrates. Spatial beam shaping is utilized for process optimization. Characterization of the processing results is realized by different techniques such as the optical Ca-test as the ""gold standard"" and Hyperspectral imaging (HIS) as a novel, fast and contact-free method.