Development and Integration of Stretchable Electronic Components into Light-Emitting Devices.pdf

Flexible and stretchable electronics are the new format of electronics that remain functional with mechanical bending, twisting, and stretching. These new kinds of devices are expected to open up new opportunities and uses by reforming the way we interact with electronics and fundamentally change our life. To reach these goals, we must move beyond conventional hard, inorganic materials such as glass and silicon and find ways to incorporate electrical function into soft materials that are flexible or even stretchable. This thesis focuses on the development of compliant electronic components including transparent conductive electrodes, light-emitting materials, and metallic electrodes, and their integration into soft light-emitting devices. Chapter 2 reports a new and simple method using shadow masks to produce flexible and stretchable patterned silver nanowire (AgNW) coatings. We easily obtain a variety of geometries and resolutions of the patterns using different shadow masks. These coatings are highly conductive and transparent and exhibit high flexibility, stretchability, and mechanical robustness. We demonstrate their use as electrodes in light-emitting electrochemical cells (LEECs) and show that these devices function during bending. However, due to the high permeability of PDMS substrate, water and air in ambient condition easily penetrate through the substrate and corrode AgNW network to form less conductive particles or rods, making it not suitable for long-term stable applications. To solve this challenge, Chapter 3 reported the fabrication of a chemical stable AgNW composite by simply replacing the highly permeable PDMS substrate with a new airtight material—transparent butyl rubber. The resulting coatings very well maintain their optical, electrical, and mechanical properties when exposing to extremely harsh conditions such as underwater or acidic vapor. Chapter 4 investigates a feasible method to fabricate a stretchable light-emitting material with an improved optical performance by mixing an ionic transition metal complex with an elastic graft copolymer and an ionic conductor. The graft copolymer not only provides the stretchability by its elastic backbone but also acts as ion hosting materials due to its ion trapping side chains. We demonstrate that devices made from this material emit bright yellow light and keep emitting light under repetitive strain cycles. Chapter 5 describes a new, simple, low-cost solution-based scalable method to produce patterned gold film with microcontact printing on elastomeric polydimethylsiloxane (PDMS). This solution-based method enables the metal deposition on not only flat surfaces but also any other irregular shapes. Additionally, the patterning method is also compatible with uneven surface due to the high comfortability of PDMS. Unlike traditional physical vapor deposited gold films that experience electrical failure at very low strain (~1%), our gold films still remain highly conductive at 90% elongations