We compare different pulse durations, modes and repetition rates of infrared ultrashort pulses lasers for the inscription of printed electronics sensors under 100 μm scale. We investigate pulse widths varying from 200 fs up to 10 ps, and standard single pulse versus 5 GHz burst regimes to produce the most efficient and cleanest ablation. The aim of the investigated process is to ablate a layer of conductive material like carbon, NiAl or NiCr forming the electronic track contours, without damaging the support which is made of a dielectric insulator. Depending on the materials and substrates of the printed electronics circuits, we have observed that 10 ps pulses in GHz burst regime with moderate individual pulse energy (around 10 μJ) have a lot of potential for an efficient production.
Part of the light rays generated within a luminescent medium with a higher refractive index than that of the
exit medium, typically air, undergo total internal reflection phenomenon (TIR); these rays will be trapped and
guided into the emissive material and will not be extracted out of an OLED device for instance. Trapped light
is reabsorbed and eventually converted into heat that will be detrimental to the device performance and
lifetime. The amount of trapped energy is highly dependent on the values of the refractive indices involved in
the multilayer stack constituting the light emitting device. The amount of trapped energy can be extensive and
can even reach as much as 75% in certain cases. Solutions to improve the outcoupling efficiency are therefore
attractive. In this paper we propose to use laser speckle to produce a random surface with controlled
parameters to enhance the OLED outcoupling. A laser speckle pattern is transferred onto a photoresist which
will be subsequently converted into a surface relief profile. The optical setup parameters drive the properties
of such surface and thus the outcoupling properties. The resulting surface has a quasi-random shape which
could be assimilated to a corrugated surface. We will show that these typical surfaces exhibit light extraction
enhancement properties. The generated pattern is then transferred onto the exit interfaces of the emitting
device. An extraction improvement close to a factor 3 is measured. We finally discuss a practical case for
which the laser speckle shape is applied to texture the surface of encapsulating cover glasses in a top-emitting
OLED on steel substrates.
Large-area top-emitting PIN structure (highly p- and n- type doped transport layers for electrons and holes and an undoped emitter layer)-organic light-emitting diode (OLED) on advanced metal foils were fabricated for lighting applications. ArcelorMittal has developed a new surface treatment on metal foils, suitable for roll-to-roll production and dedicated to large-area device integration. Both monochromatic and white devices are realized on advanced metal foils. Power efficiencies at 1000 cd/m2 of >70 lm/W (green), moreover, power efficiency of white devices of >22 lm/W are achieved. Furthermore, first large-area 60 × 60 cm white OLED sources on metal foils are presented.
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