Efeito da histerese nas propriedades elétricas em perovskitas híbridas

Abstract

The current need in society is the production of clean energy from renewable sources, and solar panels have been prominent in this aspect. Perovskite has been the subject of intense research for application in photovoltaic cells, due to its ion conduction properties and high conversion efficiency, with perovskite solar cells achieving efficiencies exceeding 25%. However, there are challenges related to the stability and capacitive effects of perovskite. Current-voltage measurements have shown that CH₃NH₃PbI₃ perovskite exhibits ferroelectric behavior and displays the phenomenon of electrical hysteresis. This phenomenon occurs due to the intrinsic polarization in the crystal structure of this perovskite, originating from the polarized methylammonium molecule. The synthesis process has a significant influence on the intensity of hysteresis, as it affects the formation of the grains that compose the film. Variations in film thickness and the volume of anti-solvent used to initiate crystallization have an impact on polarization, thus affecting the intensity of hysteresis. It is observed that the formation of larger grains in perovskite has a dual impact. On one hand, it intensifies the capacitive effect, which can be disadvantageous in terms of electrical performance. On the other hand, larger grains can also improve the efficiency in photovoltaic devices. This is because larger grains provide greater electronic connectivity, reduce transport barriers, and minimize undesired charge recombination. Therefore, there is a trade-off to be considered between the capacitive effect and efficiency in photovoltaic devices when optimizing the grain size in perovskite.