This work describes the transient phenomena that occur in hybrid CH3NH3PbI3 perovskite by measurement of the decay of a photovoltage. This analysis is important in order to understand the coupled electronic-structural phenomena that take place in the operation of the perovskite solar cell when the external influences of voltage and illumination are modified. The study also aims to reveal fundamental insights about the photovoltaic mechanisms of this unique material. The results of our analysis show a separation of the decay stages into two distinct phenomena. Firstly, there are rapid electronic transients in the ms time scale, which are ordinary response times in all kind of solar cells. The novel behaviour is a slow decay in the long time 10-100 s timescale that shows a power law decay that is common in cooperative relaxations as those occurring in polymers and glassy materials. These effects evidence that the perovskite undergoes slow changes in adaptation to external perturbations, very likely associated to the ferroic behaviour of these perovskites. These finding are important for a general analysis of the perovskite and other ferroic solar cells, as these cells have an important degree of freedom, that is the internal state of polarization, that was absent in previous photovoltaic technologies.
Depolarization kinetics of perovskite solar cells in slow time regime2 02 2015
Energy Environ. Sci., 2015, DOI: 10.1039/C4EE03171G