Light incoupling & optical optimisation of organic solar cells
Optical Nanostructures for Photovoltaics, PV 2010 (2010)
Abstract:
© Optical Society of America. Small-molecule organic solar cells (OSC) are developing towards maturity. For top-illuminated devices, device optimisation and tandem OSCs, interference effects, light trapping and thin film optics are decisive for optimal utilisation of the absorbing layers. We present transparent capping layers that allow for reduced external reflection and improved light incoupling when used in combination with thin metal top contacts. Similarly, transparent spacer layers are used in tandem devices to place the subcells at specific positions in the stack such as to utilise optical field maxima. The results are solar cells with high transparency in the visible region of the light spectrum and as well as world record tandem devices.On the communication of scientific data: The Full-Metadata Format
Computer Physics Communications 181:3 (2010) 651-662
Abstract:
In this paper, we introduce a scientific format for text-based data files, which facilitates storing and communicating tabular data sets. The so-called Full-Metadata Format builds on the widely used INI-standard and is based on four principles: readable self-documentation, flexible structure, fail-safe compatibility, and searchability. As a consequence, all metadata required to interpret the tabular data are stored in the same file, allowing for the automated generation of publication-ready tables and graphs and the semantic searchability of data file collections. The Full-Metadata Format is introduced on the basis of three comprehensive examples. The complete format and syntax are given in the appendix. © 2009 Elsevier B.V. All rights reserved.Improved photon harvesting by employing C70 in bulk heterojunction solar cells
Proceedings of SPIE - The International Society for Optical Engineering 7725 (2010)
Abstract:
To achieve higher efficiencies in organic solar cells, ideally the open circuit voltage (V), fill factor (FF) as well as the short current density (J) have to be further improved. However, only a few suitable acceptor molecules, e.g. C, are currently available for the photoactive layer. Despite a good electron mobility on the order of 1×10 cm/Vs the absorption of C in the visible sun spectrum is low. From polymer based solar cells it is known that the fullerene derivative [70]PCBM used in the photoactive layer shows a significant enhancement in J compared to [60]PCBM. This work investigates the application of fullerene C as acceptor in comparison to the well known C in vacuum processed small molecule solar cells. C shows a broadened and red shifted absorption (abs. maximum around 500 nm) compared to C. By fabricating p-i-i solar cells we show that the stronger absorption of C leads to enhanced photon harvesting and increased external quantum efficiency. The bulk heterojunction p-i-i solar cell containing C as acceptor and ZnPc as donor, co-evaporated with an optimized ratio of 2:1, and a layer thickness of 30 nm shows improved solar cell parameters: a 30% larger photocurrent of 10.1 mA/cm is obtained. The V of 0.56 V and FF of 55% remain comparable to C-containing p-i-i solar cells. Therefore, the solar cell performance is mainly improved by J and leads to a mismatch corrected power conversion efficiency of 3.12%. Thus, we show that C is an alternative fullerene to C for solar cell applications. © 2010 Copyright SPIE - The International Society for Optical Engineering.Light Incoupling & Optical Optimisation of Organic Solar Cells
Optica Publishing Group (2010) pwd5
Verantwortung der Wissenschaftler gegenüber der Gesellschaft
Chapter in Gerechtigkeit und Verantwortung in der Klima- und Energiepolitik, MV-Verlag (2010)