Harald Ade
Department of Physics
North Carolina State University

The influence of molecular orientation on organic bulk heterojunction solar cells

Location: EB1 Room 1011

Friday, February 21st 2014 - 11:00 am

In bulk heterojunction (BHJ) organic photovoltaics (OPVs), electron donating and electron accepting materials form a distributed network of heterointerfaces in the photoactive layer where critical photo-physical processes occur. However, little is known about the structural properties of these interfaces due to their complex 3-dimensional arrangement and the lack of techniques to measure local order. I will present results that show that molecular orientation relative to donor/acceptor heterojunctions is an important parameter in realizing high-performance fullerene-based, BHJ solar cells [1]. Using resonant soft X-ray scattering [2], my group characterizes the degree of molecular orientation, an order parameter that describes face-on (+1) or edge-on orientation (-1) relative to these heterointerfaces. By manipulating the degree of molecular orientation through choice of molecular chemistry and processing solvent characteristics, we are able show the importance of this structural parameter on the performance of BHJ OPV devices. A complete description and theoretical modeling yet to be developed for OPVSs will have to take such molecular orientation distributions into account.

1. J. R. Tumbleston et al., Nature Photonics, (in press) (2014).
2. B. A. Collins et al., Nat. Mater. 11, 536 (2012).

A native of Germany, H. Ade received his Ph.D. in 1990 in Physics from Stony Brook University and after a postdoc also at Stony Brook University has been a faculty at NCSU since Nov. 1992, rising through the ranks to Full Professor by 2001. He has had an active and continually funded research program and served as Director of Graduate Program in Physics from 2006-2013. Recognitions include RD100 Award, NSF Young Investigator Award, APS Fellow, AAAS Fellow, Alumni Outstanding Research Award, and Shirley Award (Advanced Light Source). He has authored more than 230 publications (h=44) and delivered more than 200 invited presentations. Amongst other professional engagements, he has served on the Scientific Advisory Committee of the BESSY-II Synchrotron Facility in Berlin, Germany, and the Helmholz Zentrum Berlin, Germany, and is presently serving on the Scientific Advisory Committee of the Advanced Light Source in Berkeley.

North Carolina State University