Thursday, October 3, 2013
3:00 PM - 4:00 PM
Where: Ryan Hall, Ryan 4003, 2190 Campus Drive, Evanston, IL 60208 map it
Audience: Faculty/Staff - Student
Dr. Bernard Kippelen of the Georgia Technological Institute will visit Northwestern to deliver an ANSER seminar entitled, "Organic photovoltaics: new strategies and old concepts"
In this talk, we will discuss the physics of organic solar cells in terms of simple equivalent circuit models and emphasize the effects of parasitic resistance effects on the current-voltage characteristics of these devices. We will show how novel device fabrication strategies based on transfer lamination can be used to minimize common limitations caused by low parasitic shunt resistance. Solar cells will be presented that operate in the photovoltaic regime when the illumination is varied by six orders of magnitude. Then, we will focus on the role of interfaces in organic solar cells and present strategies to control and stabilize the value of the work function of electrodes. A new method to produce air-stable low work function electrodes as a substitute for Ca will be presented. This method is based on surface modification by water-soluble polymers that physisorb to the surface of various conductors and lead to large surface dipoles that shift the vacuum level (> 1 eV) reducing the injection or collection barrier for electrons. We will show that these advances in interface modification can be used to design organic solar cells and modules with novel architectures that can overcome some of the economic hurdles of current approaches and accelerate the deployment of these technologies. Tandem cells with power conversion efficiencies of 8.3% have been demonstrated using these strategies with commercially available photoactive polymers. Finally, we will discuss strategies to reduce the environmental footprint of photovoltaic technologies even further.
Please contact Ria Hirsch, firstname.lastname@example.org with all questions.