Efeito do tiofeno nas propriedades de haletos de perovskitas livres de chumbo para células solares

Abstract

The use of fossil fuels results in the release of greenhouse gases, harmful to the environment, and that is why there has been a greater investment in renewable energies, specifically in solar energy because it is a clean, noiseless, and abundant source. Perovskite materials are good candidates to be used in the study of solar-to-electric energy conversion since they possess: wide absorption of solar spectrum light; compositional versatility; defect tolerance, as well as easy processing and low cost when compared to the silicon used in commercially available solar panels. Therefore, this dissertation had the purpose of investigating the properties of the inorganic perovskite with the formula Cs3Sb2I9 (CSbI), using the organic molecule thiophene (C4H4S) in the powder preparation by the antisolvent method, with the aim of examining its properties and preparing a photovoltaic device through doctor blade deposition, using a chitosan solution as a dispersant to form films to measure the ability of these materials to convert solar energy into electrical energy. By producing materials with 0%, 9%, 17%, and 34% (w/w) of thiophene [(CSbI_9), (CSbI_17), and (CSbI_34)], the additive enabled the improvement of crystallinity, as well as the suppression of secondary phases, elucidating the same crystallographic phase; it promoted the alteration of the bandgap (2.23 eV, 2.00 eV, 1.95 eV, and 2.35 eV). The DFT results confirmed the structural parameters, as well as the energy of the material in question, establishing the consistency between the theoretical and experimental methods, with crucial aspects for discussion being the crystallographic data, bandgap, and active modes in RAMAN spectroscopy. The SEM images showed that thiophene caused subtle modifications in the morphology of the precipitate – from coarse hexagonal plates to smaller needle-like and leaf-shaped particles, with a more attenuated degree of agglomeration. Supplementary EDS studies confirmed the profile for the perovskite in question, without elucidating components of the thiophene (in this case, sulfur), allowing us to understand that there is no presence of the additive post-synthesis. The RAMAN spectroscopy presented the same scattering profile for the samples, with the CSbI_9 sample showing lower scattering intensity, emphasizing a smaller quantity of phonon traps. By constructing a microcell with the FTO/TiO2/Perovskite/NiOx/Ag configuration, a PCE of 0.42% was achieved for the perovskite with a 9% additive (Voc: 0.059V; Isc=0.27mA and FF=19.37%), representing the best result compared to 0.19% with the 17% perovskite and 0.06% with 0% thiophene. The reduced gap and the lower phonon trap state due to the electron-phonon effect made CSbI_9 the best device constructed. The results provide prospects for the study of additives in modulating the properties of inorganic materials for solar cells, as well as the exploration of new methods for thin-film deposition.