Overlapping Nanostacks Enable Direct Printing of Freeform Organic LEDs

A custom-built laser-induced forward transfer (LIFT) setup was developed to fabricate multimaterial organic light emitting diode
(OLED) stacks under ambient laboratory conditions without the use of a cleanroom or encapsulation. The process enables precise
control of layer thickness through parameter tuning as confirmed by vertical scanning interferometry (VSI), yielding smooth and ho-
mogeneous layers with surface roughness values down to 2.78 nm and tunable thicknesses between 19 nm and 45 nm. A three-layer
OLED stack (total thickness ≈ 90 nm) was printed and structurally characterized using focused ion beam scanning electron mi-
croscopy (FIB-SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), revealing distinct, well-defined layer bound-
aries. First functional tests demonstrated electroluminescence at 580 nm with an operational lifetime of at least 20 min. Despite the
lack of encapsulation, the OLEDs remained stable under ambient conditions with a shelf life of up to 9 days. These results confirm
the potential of LIFT as a scalable and precise tool for the additive manufacturing of flexible thin-film devices such as OLEDs, solar
cells and fuel cells