Manipulation of the Structure and Optoelectronic Properties through Bromine Inclusion in a Layered Lead Bromide Perovskite

Abstract

One of the great advantages of organic–inorganic metal halides is that their structures and properties are highly tuneable and this is important when optimizing materials for photovoltaics or other optoelectronic devices. One of the most common and effective ways of tuning the electronic structure is through anion substitution. Here, we report the inclusion of bromine into the layered perovskite [H3N(CH2)6NH3]PbBr4 to form [H3N(CH2)6NH3]PbBr4·Br2, which contains molecular bromine (Br2) intercalated between the layers of corner-sharing PbBr6 octahedra. Bromine intercalation in [H3N(CH2)6NH3]PbBr4·Br2 results in a decrease in the band gap of 0.85 eV and induces a structural transition from a Ruddlesden–Popper-like to Dion–Jacobson-like phase, while also changing the conformation of the amine. Electronic structure calculations show that Br2 intercalation is accompanied by the formation of a new band in the electronic structure and a significant decrease in the effective masses of around two orders of magnitude. This is backed up by our resistivity measurements that show that [H3N(CH2)6NH3]PbBr4·Br2 has a resistivity value of one order of magnitude lower than [H3N(CH2)6NH3]PbBr4, suggesting that bromine inclusion significantly increases the mobility and/or carrier concentration in the material. This work highlights the possibility of using molecular inclusion as an alternative tool to tune the electronic properties of layered organic–inorganic perovskites, while also being the first example of molecular bromine inclusion in a layered lead halide perovskite. By using a combination of crystallography and computation, we show that the key to this manipulation of the electronic structure is the formation of halogen bonds between the Br2 and Br in the [PbBr4]∞ layers, which is likely to have important effects in a range of organic–inorganic metal halides.

[NH3(CH2)4NH3]SnX4 (X = Br, I): Dion–Jacobson type 2-D perovskites with short interlayer spacing

“…Furthermore, 1,4-BDA in these 2D perovskites adopts partial gauche or eclipsed conformation, and we anticipate the butane chain will adopt all-anti conformation (i.e., fully staggered) at higher temperatures, as was observed in our earlier layered double perovskites with this cation, 25 and di-ammonium cations with higher number of carbons. 39 We could see broad peak like features in the DSC curves (Fig. S12 †) on heating which might be due to the expected phase transition induced by such conformational changes in 1,4-BDA.…”

Coordination Polymer Based on a Triangular Carboxylate Core {Fe(μ3-O)(μ-O2CR)6} and an Aliphatic Diamine

“…It was also shown that based on pentaiodobismutate linked by 1,6-diaminohexane bridges, it is possible to create a molecular ferroelectric semiconductor, and it is also possible to create its thin films [47]. Last year, a work was published where layered lead perovskites were studied, in which the layers were formed with protonated 1,6-diaminohexane bridges [48]. 1,6-diaminohexane can be used to obtain self-assembled hybrid layered molybdates [49], photo-electroactive indium and antimony chalcogenides [50], dynamic organic-inorganic hybrid [H 2 dahx]ZnBr 4 crystals with the ability to control phase transitions [51], and hybrid organic-inorganic borate frameworks [52].…”