Degradation of tandem solar cells: Separating matching effects from Staebler-Wronski Effect using the Power-Matching-Method

Abstract

In thin-film tandem solar cells the sub cells are usually connected in series. The inherent current-limitation needs to be considered when optimizing the efficiency, but furthermore leads to challenges when comparing the sub cells performances of differently matched tandem cells. We have introduced the PowerMatching-Method that characterizes the device not only under one standard spectrum but under various spectral distributions. By this method, the same tandem cell can be characterized under various matching conditions. Based on simulations, we demonstrate a convenient way to compare differently matched tandem solar cells. Moreover, our simulations show that the method allows distinguishing between matching effects and changes in the sub-cells properties, e.g. changes due to the Staebler-Wronski-Effect.

Analysis of the light-induced degradation of differently matched tandem solar cells with and without an intermediate reflector using the Power Matching Method

“…The light-induced degradation of the top-cell was simulated by varying the dangling-bond density from 1 Â 10 22 m À 3 to 10 Â 10 22 m À 3 . For further details on the simulations in the context of the Power-Matching-Method see [22]. The parameters for mc-Si:H, deposited at our institute, were determined in [20].…”