Moritz Riede

Abstract:

A general strategy for the in-plane structuring of organic-inorganic perovskite films is presented. The method is used to fabricate an industrially relevant distributed feedback (DFB) cavity, which is a critical step towards all-electrially pumped injection laser diodes. This approach opens the prospects of perovskite materials for much improved optical control in LEDs, solar cells and also toward applications as optical devices.

Abstract:

Recently organic tandem solar cells with record efficiency had been shown comprising identical absorber materials in both subcells. Such structures pose new challenges for characterization. The standard test methods for measuring spectral response of tandem solar cells can not be applied. The standard procedures demand for different bias illumination during measuring spectral response allowing to select the subcell being current limiting. With subcells comprising identical absorber materials, thus having identical absorption spectra, such a selection is not trivial. In this paper, we show that with the help of detailed optical simulations of such tandem organic solar cells, their characterization is possible, and we apply the proposed method to a sample structure.

Abstract:

© 2015 Published by Elsevier B.V.Understanding the relationship between the absorber layer microstructure and the power conversion efficiency is of paramount importance to further improve the efficiency of organic solar cells. Utilizing transmission electron microscopy (TEM), (photo-)conductive atomic force microscopy ((p)cAFM), 3D drift-diffusion simulations, and density functional theory, we reveal the microscopic origins of phase-separation in a blend of zinc phthalocyanine (ZnPc) and C60, used as an absorber layer in organic solar cells. By means of (p)cAFM, we observe photoconductive, circular structures at the surface, which are identified as α-ZnPc islands. Moreover, in agreement with TEM investigations, we observe photoconductive, nanorod-like structures close to the surface which we assign to β-ZnPc. Finally, we apply a 3D drift-diffusion simulation based on the morphology determined by TEM to provide a link between the different contrasts observed in pcAFM and TEM.