Moritz Riede

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.

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.

Abstract:

We present semitransparent small-molecule organic solar cells (OSC) deposited by thermal evaporation onto indium tin oxide (ITO)-coated glass substrates. The devices employ ITO-free ultrathin metal layers as top electrodes, containing 1 nm metal surfactant interlayer for improved morphology. Using a bulk heterojunction of zinc phthalocyanine and C60, sandwiched in between doped dedicated transport layers for efficient charge carrier extraction, power conversion efficiencies comparable to conventional OSC with an intransparent thick back electrode and similar device layout are achieved: the semitransparent OSC yield power conversion efficiencies well above 2% with external quantum efficiencies above 30%-40%. Organic light incoupling layers improve the transmission to up to 50% in the visible part of the optical spectrum. © 2009 American Institute of Physics.