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SKM-SYOP: SKM-Symposium Elementary Processes in Organic Photovoltaics
SKM-SYOP 1: Elementary Processes in Organic Photovoltaics
SKM-SYOP 1.1: Hauptvortrag
Montag, 14. März 2011, 10:30–11:00, TRE Ma
Charge separation in organic solar cells and the principle of detailed balance — •Uwe Rau1 and Thomas Kirchartz2 — 1IEK5-Photovoltaics, Forschungszentrum Jülich, Germany — 2Experimental Solid State Physics, Blackett Laboratory of Physics, Imperial College London, UK
The invention of the solar cell as an electro-optical power device dates back to the year 1954. In 1961, Shockley and Queisser derived the maximum conversion efficiency of an ideal pn-junction solar cell by applying the principle of detailed balance. This principle, known since the years 1924/25, is strictly valid only close to thermal equilibrium. Despite of this restriction, application of this principle to solar cells under illumination, i.e. in a non-equilibrium situation, is commonly accepted and successfully used even for the analysis of non-ideal solar cells. During the last two decades, new photovoltaic technologies like dye sensitized or organic solar cells have emerged from laboratories. The large difference of organic semiconductors to their inorganic counterparts challenges our general understanding of solar cells. The present contribution will start from the fundamentals of photovoltaic energy conversion and discuss the principles that are common to all these devices. In a next step, a general approach based on the principle of detailed balance is introduced that allows us to describe organic and inorganic solar cells and to highlight their different working principles. These differences have immediate consequences on the limitations, the practical design and the technical realization of the various types of devices.