Recently, organic-inorganic perovskite compounds have attracted much attention for applying to optical devices such as photovoltaic cells and light emitting diodes. These compounds can be prepared by various combinations of organic ammoniums and lead halides. Two-dimensinal perovskites have been widely studied owing to their excellent optical properties due to the quantum confinement effect. For obtaining two-dimensinal perovskites, ammoniums are usually introduced into organic part of perovskite compounds, and phosphoniums are rarely used in the perovskite systems. Therefore, the effects of cation type are still unclear. Furthermore, by using p-conjugated polymers instead of low molecular ammoniums and phosphoniums, interaction should be induced between organic and inorganic parts, and it is expected to develop novel physical properties. In this study, to investigate the effect of cation type and polymer introduction, we prepared perovskite compounds with alkylphosphonium and polythiophene derivatives. Poly[3-(6-bromohexyl)thiophene] (PBHT) was synthesized by the catalytic transfer polymerization method and reacted with trimethylamine and trimethylphosphine to obtain polythiophene derivatives, PC6TNBr and PC6TPBr, with alkylammonium and phosphonium side chains, respectively. Perovskite films, PC6TN-PbBr and PC6TP-PbBr, were prepared by cast method using N,N-dimethylformamide solution containing stoichiometric amount of the polythiophene derivatives and PbBr2. Perovskite films with phosphonium, C6TP-PbBr, were also prepared from alkylphosphonium, C6H13P(CH3)3Br (C6TPBr), by spin-coating method. The structures of obtained films were investigated by X-ray diffraction measurements. While C6TPBr, PC6TNBr, and PC6TPBr are amorphous, diffraction peak was observed at 5.5° for C6TP-PbBr and 3.7° for PC6TN-PbBr and PC6TP-PbBr. This suggests that new structures are formed by complexing C6TPBr, PC6TNBr, and PC6TPBr with PbBr2. The optical properties of the films were investigated by UV-vis absorption spectroscopy. Exciton absorption peaks were observed at 325 and 326 nm for PC6TN-PbBr and PC6TP-PbBr with broad absorption peak of π-π* transition. C6TP-PbBr shows exciton absorption peak at 321 nm. Perovskite compounds prepared with quaternary hexylammonium shows exciton absorption peak at 351 nm. Therefore, it was revealed that the effect of cation types is more pronounced in low molecular systems.

Fabrication of novel organic-inorganic perovskites using p-conjugated polymers: Effect of cation types and polymer introductions

2019 Fall National Meeting

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