Yang, Ehrenfreund & Vardeny , Physical Review Letters 99 , 157401 (2007)

1. Polaron Spin-lattice Relaxation Time in -Conjugated Polymers Obtained from Optically Detected Magnetic Resonance DynamicsZ. Valy Vardeny, University of Utah, DMR-0503172 We describe a method for obtaining polaron spin-lattice relaxation time TSL in -conjugated polymers by measuring the photoluminescence detected magnetic resonance (PLDMR) dynamics as a function of microwave power and laser intensity. The peculiar PLDMR dynamics is well-described by a spin dependent recombination process where both recombination and spin relaxation rates determine together the response dynamics. We apply this method to the spin ½ PLDMR in films of pristine 2-methoxy-5-(2’-ethylhexyloxy) phenylene vinylene [MEH-PPV] polymer, as well as MEH-PPV doped with various concentrations of radical impurities and magnetic nano-particles. We obtained for polarons TSL~ 30 s in pristine MEH-PPV, but substantially shorter when the magnetic impurities are added. Frequency dependence of the PL-detected magnetic resonance (PLDMR) in a -conjugated polymer film. The in-phase (I), quadrature (Q), phase (), and magnitude (M) dynamics are shown; there is a zero-crossing at frequency, f0 = 30 kHz. The inset shows the dependence of f0 on the microwave power, P. Yang, Ehrenfreund & Vardeny, Physical Review Letters 99, 157401 (2007)

2. Teaching a new graduate course on Organic Electronics at the University of Utah and outreachZ. Valy Vardeny, University of Utah, DMR-0503172 The PI, Valy Vardeny, together with Drs. Wojcik and DeLong designed and taught a new two-semester graduate course in the Physics Department of the University of Utah, in which the optical, magnetic and electronic properties of organic semiconductors were thoroughly reviewed. In 2006-07 academic year we had about 10 graduate students, and two postdocs mainly from Physics and ECE departments. The course also involves seminars given by the participants and laboratory demonstration of real organic optoelectronic devices, such as OLEDs and organic solar cells. Valy Vardeny also regularly accepts invitations to spread understanding and awareness of Organic Electronics science and technology issues. On November 2006 he gave the Hatch lecture in Chemistry at the University of Connecticut, and on May 2007 to a diverse audience at the University of Utah, New Discoveries series (SYNERGY) organized by the Vice President of Research. 2006-07 Organic Semiconductors Class at the UoU