D. Nehera, C. Yina, S. Bangea, X.H. Yanga, Thomas Kietzkeb, Hans-Heinrich Hörholdc
aUniversity of Potsdam, Institute of Physics, Am Neuen Palais 10, 14469 Potsdam, Germany.
b Institute of Materials Research and Engineering (IMRE), Research Link 3, 117602 Singapore
cUniversity of Jena, Institute of Organic Chemistry and Macromolecular Chemistry, Humboldtstr. 10, 07743 Jena, Germany
Recently, a novel approach to insert ultrahin polymer layers with well-controllable electronic properties into solution-processed optoelectronic device structures has been proposed [1]. This approach allows to establish property-function relationships, which are not accessible by the study of conventional blend device. Experiments on electrophosphorescent devices as well as Kelvin-probe experiments under illumination show that these layers are dense and exhibit a strong electron-blocking function [2,3]. Upon proper choice of the HOMO and LUMO level of the interlayer material, efficient recombination of charges at the interface could be realized. Comparable studies on bilayer and blend solar cell structures shows that the performance of these devices is not determined by charge transport and free carrier recombination [4]. This supports the view that the efficiency to form free carriers is the determining process in polymer-polymer solar cells.
[1] J. S. Kim, R. H. Friend, I. Grizzi, J. H. Burroughes, Appl. Phys. Lett. 87 (2006) 023506.
[2] X.H. Yang, F. Jaiser, B. Stiller, D. Neher, F. Galbrecht, U. Scherf, Adv. Funct. Mater. 16 (2006) 2156
[3] C. Yin, Th. Kietzke, B. Pieper, B. Stiller, D. Neher, Appl. Phys. Lett. 90 (2007) 133502
[4] C. Yin, D. Neher, Th. Kietzke, H.-H. Hörhold, Appl. Phys. Lett., 90 (2007) 092117