Transformation of PbI₂, PbBr₂ and PbCl₂ salts into MAPbBr₃ perovskite by halide exchange as an effective method for recombination reduction

Abstract

Halide perovskite derivatives present unprecedented physical phenomena among those materials suitable for photovoltaics, such as a fast ion diffusion coefficient. Here we report how to take benefit from this property during the growth of halide perovskite in order to control the morphological and optoelectronic properties of the final thin film. Using a large enough halide reservoir, the nature of the halides present in the final perovskite layer can be exchanged respect the initial salt used in the two step deposition method. In particular, we report the preparation of methylammonium lead bromide (MAPbBr 3 ) thin film using a two-step method based on the transformation of PbI 2 , PbBr 2 and PbCl 2 salts into MAPbBr 3 perovskite after dipping in a MABr solution. The films prepared from different salts present different properties in terms of morphology and optoelectronic properties, thus providing significantly different performance when they are used for the preparation of photovoltaic devices. Interestingly, the use of PbI 2 and PbCl 2 salts reduce the charge recombination and increases the obtained open circuit potential, especially in the former case. However, the highest photocurrent is obtained when PbBr 2 is used. While for PbI 2 and PbCl 2 salts no traces of the former salt are observed in the obtained MAPbBr 3 layer after 10 minutes of dipping time, the presence of PbBr 2 still been detected when this salt is employed as it has been determined by Xray diffraction.2

In Situ Vapor‐Phase Halide Exchange of Patterned Perovskite Thin Films

“…First, PbI 2 (black) exhibits a distinct peak at 2θ = 12.6°, indicating that the template-grown PbI 2 crystal domains are highly oriented in the [0001] direction. [15,19] After the primary conversion through the introduction of MAI vapor (t MAI = 15 min) to [0001]-oriented PbI 2 line patterns, we observed the emergence of the characteristic (110), (112), (220), and (310) peaks of tetragonal MAPbI 3 (filled red circles) at 2θ = 14.1°, 20.0°, 28.4°, and 31.9°, respectively. [11a,20] We note that the original [0001] peak of PbI 2 (inverted black triangles) still exists, suggesting that PbI 2 has not been entirely converted into MAPbI 3 with a 15-min MAI introduction.…”

A Redox‐Based Resistive Switching Memory Device Consisting of Organic–Inorganic Hybrid Perovskite/Polymer Composite Thin Film

“…The interplanar distance evaluated from the peak at 29.95° using Bragg equation was around 2.96 Å, verifying the d‐spacing value (2.9 Å) of the lattice obtained from SAED. It is noteworthy that two distinct major peaks located at 18.57° and 23.7°, shown with asterisk in Figure a, were appeared for both Perovskite‐20 and Perovskite‐10 films, which can be attributed to (020) and (111) planes of the PbBr 2 as a result of the retarded nucleation and crystal growth induced by PEO …”

Anions‐Exchange‐Induced Efficient Carrier Transport at CsPbBrxCl3‐x/TiO2 Interface for Photocatalytic Activation of C(sp3)−H bond in Toluene Oxidation

“…Consistent with the trend obtained in UV‐Vis absorption measurement, the PL peak shows a blue shift of ∼100 nm from CPB/Ti to CPB/Ti‐180Cl. For the CPB/Ti‐180Cl, the peaks at 495 nm and 550 nm are photoluminescence of PbBr 2 and PbCl 2 residues, [31] which may come from the excess PbCl 2 added during the anion exchange. The Cl − ions from the PbCl 2 will gradually diffuse into the perovskite lattice and replace the Br − site, and hence forming a mixture of PbBr 2 and PbCl 2 nanoparticles on the surface of heterojunction.…”