Two-Dimensional Hybrid Organohalide Perovskites from Ultrathin PbS Nanocrystals as Template

Abstract

Direct conversion of preprocessed binary semiconductor NCs as template holds the key toward the shape control of hybrid perovskites. Here we report on an innovative route for realizing shape-controlled hybrid organohalide perovskite NCs from two-dimensional PbS NCs on solid substrates. Rectangular PbI 2 NCs are first synthesized by iodination of PbS NCs. Resultant PbI 2 NCs are subsequently transformed into the well-defined rectangular hybrid perovskite NCs upon controlled CH 3 NH 3 Br exposure. Structural analyses using X-ray absorption fine structure reveal transition of cubic lattice of PbS to hybrid perovskites with a mixture of cubic and tetragonal phases exhibiting a bimodal distribution of shorter Pb−Br and longer Pb−I bonds around an immediate neighboring lead absorber within the first coordination shell. This direct all anion exchange reaction route opens up new strategies for the fabrication of shape-controlled perovskite NCs on flexible substrates from suitable existing binary NCs as template for optoelectronic applications.

Vacancy-Mediated Anion Photosegregation Kinetics in Mixed Halide Hybrid Perovskites: Coupled Kinetic Monte Carlo and Optical Measurements

“…A Monte Carlo-derived movie illustrating this can be found in the SI (Movie S1). The predicted core/shell structure may be detected using techniques sensitive to the local halide ion environment such as X-ray absorption near-edge spectroscopy …”

“…The predicted core/shell structure may be detected using techniques sensitive to the local halide ion environment such as X-ray absorption near-edge spectroscopy. 38 Perhaps one of the more intriguing results of these Monte Carlo simulations is evidence of trapped Br − within the I-rich core. Because most vacancies have been expelled from the Irich core, Br − ions still within the I-rich domain have difficulty escaping.…”

Bandgap Tuning of Silver Bismuth Iodide via Controllable Bromide Substitution for Improved Photovoltaic Performance

“…During the rapid development of lead perovskite, CH 3 NH 3 PbI 3 ((MA)­PbI 3 ) has been the most investigated material, but not only the pure compound. For example, iodide can be replaced by bromide totally or partially, which has been reported in several publications. − As a result, the bandgap of mixed-halide perovskites can be tuned over the range 1.6–2.3 eV, which is very appealing for absorption optimization, especially for tandem solar cells which require components with larger bandgap. Besides, the change in composition might induce changes in crystal structure, crystal growth process, and electrical properties, which finally could provide a striking enhancement in PCE and stability of solar cells.…”

Towards environmental friendly multi-step processing of efficient mixed-cation mixed halide perovskite solar cells from chemically bath deposited lead sulphide

“…The deposited PbS was a 75 nm thick film introduced as a precursor material to be subsequently converted into the final perovskite layer 26 . Successive exposure to iodine vapor and methylammonium bromide was used to directly convert two-dimensional (2D) PbS nanocrystals into nanocrystals of hybrid perovskite maintaining 2D morphology 38 . Radio-frequency sputtering assisted solution process has also been employed for depositing PbS films which were converted into the perovskite layer by exposing in an iodine atmosphere at room temperature, followed by immersing in a methylammonium iodide solution to be transformed to the perovskite layer 27 .…”