Dissertation Defense

Charge and Exciton Dynamics in Organic Optoelectronic Devices

Caleb CoburnPhD CandidateUniversity of Michigan Physics Department

Organic optoelectronics use carbon based molecules to interface between light and electrical signals. The operation of these devices is determined by the dynamic behaviors of their charges and excited states. For example, organic light emitting diodes use injected electrical charges to form excited states that, in turn, emit light. Organic photovoltaics and photodetectors operate by the reverse process. Understanding the dynamics of charges and excited states is crucial to designing high performance devices.

The first part of this thesis focuses on understanding charge and exciton dynamics in organic light emitting devices. First, charge balance and exciton connement are studied using sensitizer methods and analytical modeling. The impact of changes in charge balance and exciton connement on the lifetime of blue phosphorescent organic light emitting diodes is investigated. The understanding gained in these studies is then applied to the design of a highly reliable stacked white-emitting device for solid state lighting.

The second part focuses on charge diusion in organic heterostructures. Because of the low charge mobilities of organic semiconductors, organic devices are typically thin with negligible lateral charge transport. We show that charge can be transported laterally across centimeters in certain organic heterostructures and explain the properties of the heterostruture that give rise to this phenomena. Lateral transport heterostructures are then used to develop the first organic charge coupled devices.

Sponsored by

OCM Group

Faculty Host

Stephen Forrest