Breaking down the reverse bias breakdown of perovskite solar cells

Abstract

In a partially shaded photovoltaic module, the shaded cells experience reverse bias conditions that may lead to significant degradation, especially in perovskite solar cells. A thorough understanding of the behavior of perovskite solar cells under reverse bias is therefore required for designing modules that are suitable for outdoor operation.
This thesis combines literature data with experimental results obtained from spin-coated, planar inverted perovskite solar cells.
In the first part of the thesis, measurement parameters and a definition of the breakdown voltage are proposed. The resulting breakdown voltages can be used as scaling factor to correct cell-to-cell variation in the reverse bias behavior. In the second part of this thesis, the effects of illumination on the reverse bias behavior are explained through a mechanism based on ion migration and an electrochemical reaction. Additionally, an imaging technique (ReBEL) is introduced and employed to reveal that two distinct breakdown mechanisms occur, depending on the current injection level.
These findings indicate that further research is required to gain a complete understanding of the reverse bias behavior of perovskite solar cells. However, by standardizing measurement procedures, investigating the breakdown mechanisms, and developing novel characterization techniques, meaningful progress towards stable perovskite modules can be achieved.