Grafted poly(phenylene-ethynylene) : optical and optoelectronic applications

Abstract

Poly(phenylene-ethynylene) (PPE), a fully conjugated polymer system, exhibits high solution state quantum yields, narrow emission profiles, and wide band gaps allowing for blue emission, making them ideal candidates for display applications. Unfortunately, PPEs have received little attention in solid-state optical and optoelectronic applications due to aggregation phenomena, which significantly reduces solid-state emission efficiencies and limits the miscibility of PPEs with other materials systems. Furthermore, the acetylene linkage in PPEs limits the redox properties of these polymers making charge injection, especially holes, difficult without material degradation. However, this dissertation details the development of a grafted PPE system that demonstrates enhanced optical and optoelectronic behavior by circumventing the negative aspects of traditional PPEs outlined above. The basic luminescent properties of conjugated polymer systems are outlined in Chapter 2. Building upon this fundamental understanding, we move to the design and synthesis of a new grafted PPE system described in Chapter 3. The synthetic modification of the PPE is used for domain-specific incorporation into a cylindrical morphology block copolymer host matrix, which is reported in Chapter 4. This work also details the design and fabrication of new PPE based organic light emitting devices (OLEDs). Chapter 5 discusses the development of a new hybrid OLED system whereby energy transfer from a hole-transport host to grafted PPEs results in efficient, blue PPE electroluminescence (EL) that matches the solid-state PL. Moreover, the grafting process is completely modular, allowing for further modification.

(cont.) Chapter 6 details the introduction of a charge transport moiety, which is directly grafted to a PPE backbone structure, enabling an entirely polymeric, single layer device, capable of achieving efficient, narrow blue EL. The culmination of these results in Chapter 7 solidifies that PPEs, in combination with a modular grafting technique, can now be accessed as viable light-emitting materials for OLED applications.