Structure-Function-Property Relationships inConjugated Polyelectrolytes (CPEs)

Thuc-Quyen Nguyen, University of California-Santa Barbara, DMR 0547639 The aim of this project is to understand structure-function-property relationships in CPEs. Our goal is to optimize the materials function and properties by a systematic study that incorporates new materials design, a range of processing options and characterization techniques. We studied the charge transport properties of CPEs as a function of the conjugated backbone and charge reversal (cationic versus anionic). These materials are used as an electron transporting layer in polymer light-emitting diodes (PLEDs). More efficient electron injection from Al and better device performance are attained with the CPE bearing negative charges. For cationic CPEs having the same counterion but different conjugated structure, one observes better device efficiency using the material with higher electron mobility. Thus, both charge and backbone are important for optimizing device performance. The result is significant because now the fabrication of organic LEDs with excellent performance does not need to rely on unstable metals, such as calcium or barium. Future plan: We will investigate the chemical structures of the charge and the side group and the length of the side group influencing the optical and charge transport properties of CPEs.

CathodeCharged CP

MEH-PPVHIL: PEDOT

Glass/ITO anode10

-2

10-1

100

101

102

103

104

Lum

inan

ce (C

d/m

2 )

12008004000

Current Density (mA/cm2)

Ba/Al

Al

PFSO3-Na+/Al

PFN+Br-/Al

PFBTN+Br-/Al

PFBTN+Br- 1.0 10-7 cm2/V.s

PFN+Br- 1.2 10-5 cm2/V.s

PFSO3-Na+ 1.2 10-8 cm2/V.s

Mobility,

Mentoring Young Students and Outreach Thuc-Quyen Nguyen, UCSB, DMR-0547639

This summer, the PI had four undergraduate students working in her laboratory: Jennifer Sift (UCSB), Jason Lin (UCLA), Manuel Schnabel (Oxford University), and Victoria Crockett (Jackson State University). Each focused on different aspects of materials from materials processing to characterization at the nanoscale and in bulk to device fabrication. The research experience is a key factor in students’ decisions to pursue advanced degrees in science and engineering. Jason Lin, Jennifer Sift, and Victoria Crockett plan to attend graduate schools. The PI led the “Ask a Scientist” section for the NanoQuest Day at UCSB. This event was organized by the The National Nanotechnology Infrastructure Network (NNIN) Education Program. There were 34 middle school students and 3 teachers from Tehachapi, CA participating in the event to learn various aspects of nanoscience and nanotechnology. The PI participated in “Science Night” at local middle schools. She introduced various types of materials and their applications to young students, parents, and teachers (Bottom picture). The PI is a guest speaker and a member of the planning board for the Women in Science and Engineering (WiSE) at UCSB. WiSE promotes equal opportunity for women and girls in science and engineering and supports their scientific and career advancement.

The PI discussed organic semiconducting materials with her summer intern students: Jason Lin, Manuel Schnabel, and Victoria Crockett.