Young Investigators Seminar
◥Title: Studies of Solution-Processed Organic Light-Emitting Diodes (OLEDs) and Non-Fullerene Based Organic Photovoltaics (OPVs)
◥Speaker: Dr. Taeshik Earmme (Department of Chemical Engineering, University of Washington)
◥Date: 13 October, 2014 (Mon) 11:00-12:00
◥Place: #1101 @ W1-3 Building
Organic electronics, commonly referred as plastic electronics, is an emerging technology for addressing many challenges that our society is facing. Over the past two decades, organic electronics has gained enormous attention due to its many advantages, including low power consumption, low-cost, scalable, and flexible design. Development of high-performance devices by designing new materials and related device engineering is crucial to the future advances in organic electronics. My talk will focus on studies of two classes of optoelectronic devices, organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs), fabricated by solution-processing of organic semiconductors, and aims to better understand structure-property-performance relationships resulting from solution-based fabrication.
Studies of dendritic oligoquinolines were found to be promising new electron-transport materials (ETMs) for high-performance phosphorescent OLEDs (PhOLEDs). Solution-processed multilayered blue PhOLEDs with orthogonal solution-processed ETMs were found to have the highest efficiency observed among polymer-based devices at the time. The surface morphology and charge-transport properties of the ETMs were successfully tuned by solution-deposition, which made it possible to eliminate the need for interfacial materials and low work function metals commonly used as cathode materials in OLEDs. High-performance solution-processed PhOLEDs using commercial ETMs were also demonstrated using orthogonal solution-processing. The bulk conductivity and charge transport properties of ETMs were enhanced by a novel solution n-doping with alkali metal salts.
Non-fullerene acceptor based organic bulk heterojunction (BHJ) solar cells were also developed and studied. Solution-processed polymer/polymer blend solar cells using new acceptor copolymers were investigated and found to be the most efficient all-polymer solar cells reported to date. Controlling polymer blend morphology by solution-processing from a co-solvent system also led to further enhancement of device performance. In addition, novel n-type small-molecules were investigated and demonstrated as promising acceptors for efficient non-fullerene BHJ OPVs. Device performance of the developed polymer/polymer solar cells and polymer/non-fullerene acceptor solar cells even exceeded that of corresponding polymer/fullerene BHJ solar cells. The results suggest that the development of non-fullerene based organic photovoltaics can be a promising strategy for future renewable energy sources.