Organic solar cell modules for specific applications—From energy autonomous systems to large area photovoltaics M. Niggemann a,b, ⁎ , B. Zimmermann b , J. Haschke a , M. Glatthaar a,b , A. Gombert a a Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraβe 2, 79110 Freiburg, Germany b Freiburg Materials Research Centre, Stefan-Meier-Straβe 21, 79104 Freiburg, Germany, Available online 6 March 2008 Abstract We report on the development of two types of organic solar cell modules one for energy autonomous systems and one for large area energy harvesting. The first requires a specific tailoring of the solar cell geometry and cell interconnection in order to power an energy autonomous system under its specific operating conditions. We present an organic solar cell module with 22 interconnected solar cells. A power conversion efficiency of 2% under solar illumination has been reached on the active area of 46.2 cm 2 . A voltage of 4 V at the maximum power point has been obtained under indoor illumination conditions. Micro contact printing of a self assembling monolayer was employed for the patterning of the polymer anode. Large area photovoltaic modules have to meet the requirements on efficiency, lifetime and costs simultaneously. To minimize the production costs, a suitable concept for efficient reel-to-reel production of large area modules is needed. A major contribution to reduce the costs is the substitution of the commonly used indium tin oxide electrode by a cheap material. We present the state of the art of the anode wrap through concept as a reel-to-reel suited module concept and show comparative calculations of the module interconnection of the wrap through concept and the standard ITO-based cell architecture. As a result, the calculated overall module efficiency of the anode wrap through module exceeds the overall efficiency of modules based on ITO on glass (sheet resistance 15 Ω/square) and on foils (sheet resistance 60 Ω/square). © 2007 Elsevier B.V. All rights reserved. Keywords: Organic solar cell; Module; Indoor; Bulk heterojunction; Large area; Micro contact printing 1. Introduction Low material and production cost, mechanical flexibility and low weight are the most often named promising properties of organic solar cells. These properties give rise to a large range of possible applications for photovoltaics. To enter the markets, the competition with established solar cell technologies has to be faced and therefore the specific solar cell technology has to be adapted to the specific requirements. The low weight and the aspired mechanical flexibility of polymer foil can be a precondition to enter niche markets, e.g. the integration of photovoltaic cells into smart clothing [1]. Organic solar cells have the potential to be competitive on the photovoltaic power market due to the expected low production costs even with lower efficiencies and shorter lifetimes as their inorganic counterparts. In this paper we address two types of solar cell modules. The first is based on the commonly used transparent indium tin oxide (ITO) electrode and is regarded as an intermediate step towards niche applications for organic solar cells. The module is dimensioned such that an output voltage of 4–5 V is achieved under indoor illumination. Possible applications are low power consumer products and energy autonomous monitoring systems as well as in combination with organic light emitting diodes. The production technologies for this type of solar cells are still under development. Different techniques like screen printing [2] and laser scribing [3] for the patterning of the functional layers have been investigated by other groups. We propose micro contact printing of a self assembling monolayer for the patterning of the polymer anode. This method allows to employ highly efficient coating techniques and prevents the contamina- tion of the polymer anode by subsequent structuring process. Available online at www.sciencedirect.com Thin Solid Films 516 (2008) 7181 – 7187 www.elsevier.com/locate/tsf ⁎ Corresponding author. Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraβe 2, 79110 Freiburg, Germany. Tel.: +49 761 2034798; fax: +49 761 2034801. E-mail address: michael.niggemann@ise.fhg.de (M. Niggemann). 0040-6090/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2007.12.093