Dispersing an ionic transition metal complex into an elastomeric matrix enables the fabrication of intrinsically stretchable light-emitting devices that possess large emission areas (∼175 mm(2)) and tolerate linear strains up to 27% and repetitive cycles of 15% strain. This work demonstrates the suitability of this approach to new applications in conformable lighting that require uniform, diffuse light emission over large areas.
We present new flexible, transparent, and conductive coatings composed of an annealed silver nanowire network embedded in a polyurethane optical adhesive. These coatings can be applied to rigid glass substrates as well as to flexible polyethylene terephthalate (PET) plastic and elastomeric polydimethylsiloxane (PDMS) substrates to produce highly flexible transparent conductive electrodes. The coatings are as conductive and transparent as indium tin oxide (ITO) films on glass, but they remain conductive at high bending strains and are more durable to marring and scratching than ITO. Coatings on PDMS withstand up to 76% tensile strain and 250 bending cycles of 15% strain with a negligible increase in electrical resistance. Since the silver nanowire network is embedded at the surface of the optical adhesive, these coatings also provide a smooth surface (root mean squared surface roughness<10 nm), making them suitable as transparent conducting electrodes in flexible light-emitting electrochemical cells. These devices continue to emit light even while being bent to radii as low as 1.5 mm and perform as well as unstrained devices after 20 bending cycles of 25% tensile strain.
The
emergence of flexible and stretchable optoelectronics has motivated
the development of new transparent conductive electrodes (TCEs) to
replace conventional brittle indium tin oxide. For modern optoelectronics,
these new TCEs should possess six key characteristics: low cost, solution-based
processing; high transparency; high electrical conductivity; a smooth
surface; mechanical flexibility or stretchability; and scalable, low-cost
patterning methods. Among many materials currently being studied,
silver nanowires (AgNWs) are one of the most promising, with studies
demonstrating AgNW films and composites that exhibit each of the key
requirements. However, AgNW-based TCEs reported to date typically
fulfill two or three requirements at the same time, and rare are examples
of TCEs that fulfill all six requirements simultaneously. Here, we
present a straightforward method to fabricate AgNW/polymer composite
films that meet all six requirements simultaneously. Our fabrication
process embeds a AgNW network patterned using a solution-based wetting–dewetting
protocol into a flexible or stretchable polymer, which is then adhered
to an elastomeric poly(dimethylsiloxane) substrate. The resulting
patterned AgNW/polymer films exhibit ∼85% transmittance with
an average sheet resistance of ∼15 Ω/sq, a smooth surface
(a root-mean-square surface roughness value of ∼22 nm), and
also withstand up to 71% bending strain or 70% stretching strain.
We demonstrate the use of these new TCEs in flexible and stretchable
alternating current electroluminescent devices that emit light to
20% bending strain and 60% stretching strain.
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