Electroluminescence, Stabilization, Perovskite, Solar Cell
Summary / Abstract:
We have used electroluminescence to evaluate short-term stabilization process of perovskite solar cells. The cells were kept in the dark between periodic characterization sessions. In a characterization session, a cell was forward biased with a quarter of short circuit current density, while voltage was continuously logged and electroluminescence (EL) images were acquired. When a constant current forward bias was applied, the voltage on all cells immediately jumped to a certain level and then it gradually stabilized to a voltage around 1 V over the course of one to several minutes. Similar stabilization was observed for intensity of EL images. Based on the observed behaviour we differentiated four different stabilization types: positive exponential decay, overshoot, exponential rise continued with linear rise, and deficit. During the first three, the temporal EL emission can be predicted from applied voltage using reciprocity relation. However, during the deficit stabilization, the EL intensity, calculated from applied voltage, initially misses the measured EL intensity forming a kind of EL deficit. The observed stabilization processes were both, positive and negative. Spatial information from EL images reveals that when there is no EL deficit, the images mostly just change in intensity, but when EL deficit is present, the (in)homogeneity of the images also changes.