Materiais de Perovskita com aplicação em células solares

Ruddlesden-Popper perovskites, a type of layered material, have been known for a long time, but only recently these materials have gained special attention from the optoelectronics community. This reemergence is mainly due to recent studies in hybrid lead halide perovskites that show outstanding potential for solar energy conversion. In this work, we demonstrate a simple synthesis of stable Ruddlesden-Popper perovskite with general formula L2[FAPbI3]n-1PbI4 (L = butylammonium or benzylammonium; FA = formamidinium; and n = 1 or 2). With this synthetic approach, we obtain a printable perovskite paste or a powder suitable for solution-process methods, which are desirable for optoelectronic devices. In spite of the simplicity of the synthesis and stability of these perovskites, the photoluminescence of the n=2 materials present severe changes and unexpected features. To better understand their structure and photophysical behavior, besides the conventional spectroscopic techniques, we used in situ SAXS, in situ GIWAXS, and TGA experiments. We demonstrate that the butylamine-based material (BA2[FAPbI3]PbI4) has a fast growth kinetics and form a stable pure-phase Ruddlesden-Popper perovskite. In contrast, due to a slightly rougher synthetic condition, the benzylamine-based material (BLA2[FAPbI3]PbI4¬) seems to have a higher density of defects states. We have attributed these unexpected emission features to the formation of thicker quantum-wells and to self-trapped excitons, originated from defects and phonon modes in the crystal lattice. We, then, demonstrate the applicability of these materials by fabricating solar cells: despite the limited performance, the devices showed positive outputs and gave us perspectives for future works (AU)