Building Blocks of Hybrid Perovskites: A Photoluminescence Study of Lead‐Iodide Solution Species
Oleksandra Shargaieva, Lena Kuske, Jörg Rappich, Eva Unger, N. H. Nickel
Abstract
Abstract In this work, we present a detailed investigation of the optical properties of hybrid perovskite building blocks, [PbI 2+n ] n− , that form in solutions of CH 3 NH 3 PbI 3 and PbI 2 . The absorbance, photoluminescence (PL) and photoluminescence excitation (PLE) spectra of CH 3 NH 3 PbI 3 and PbI 2 solutions were measured in various solvents and a broad concentration range. Both CH 3 NH 3 PbI 3 and PbI 2 solutions exhibit absorption features attributed to [PbI 3 ] 1− and [PbI 4 ] 2− complexes. Therefore, we propose a new mechanism for the formation of polymeric polyiodide plumbates in solutions of pristine PbI 2 . For the first time, we show that the [PbI 2+n ] n− species in both solutions of CH 3 NH 3 PbI 3 and PbI 2 exhibit a photoluminescence peak at about 760 nm. Our findings prove that the spectroscopic properties of both CH 3 NH 3 PbI 3 and PbI 2 solutions are dominated by coordination complexes between Pb 2+ and I − . Finally, the impact of these complexes on the properties of solid‐state perovskite semiconductors is discussed in terms of defect formation and defect tolerance.