Methylammonium lead iodide (MAPbI3–x
Cl
x
)
thin films were synthesized
using chemical vapor deposition. Temperature-dependent grazing incidence
synchrotron-based X-ray diffraction measurements confirm that the
structure of MAPbI3–x
Cl
x
, where Cl acts more like a dopant, remains throughout
in the tetragonal phase in the temperature range of 20–300
K. These studies are further correlated with temperature-dependent
photoluminescence (PL) studies. The PL peak energy monotonically increases
with temperature, suggestive of a single-phase behavior. Resistance
measurements conducted as a function of temperature show an absence
of inflection points, suggesting uniformity in its phase. Between
200 and 325 K, the resistance remains a constant.
The strong spin–orbit coupling (SOC) in lead halide perovskites, when inversion symmetry is lifted, has provided opportunities for investigating the Rashba effect in these systems. Moreover, the strong orbital moment, which, in turn, impacts the spin-pair in singlet and triplet electronic states, plays a significant role in enhancing the optoelectronic properties in the presence of external magnetic fields in lead halide perovskites. Here, we investigate the effect of weak magnetic fields (<1 T) on the photoluminescence (PL) properties of [Formula: see text] nanocrystals with and without Ruddlesden–Popper (RP) faults and single crystals of [Formula: see text]. Along with an enhancement in the PL intensity as a function of an external magnetic field, which is observed in both lead bromide perovskites, the PL emission red-shifts in [Formula: see text] nanocrystals. Density-functional theory calculations of the electronic band-edge in [Formula: see text] show almost no change in the energy gap as a function of the external magnetic field. The experimental results, thus, suggest the role of mixing of the triplet and singlet excitonic states under weak magnetic fields. This is further deduced from an enhancement in PL lifetimes as a function of the field in [Formula: see text]. In [Formula: see text], an increase in PL intensity is observed under weak magnetic fields; however, no changes in the peak energy or PL lifetimes are observed. The internal magnetic fields due to SOC are characterized for all three samples and found to be the highest for [Formula: see text] nanocrystals with RP faults.
Sequential low-pressure chemical vapor deposition (CVD) offers a controllable and scalable route for the conformal growth of Pb-based perovskite materials, with an improved environmental stability and control of the phase stability of the material. Reducing the dimensionality of the material and alloying with Sn have the additional benefit of mitigating both the instability and environmental challenges associated with Pb. Herein, we report on the sequential CVD of a two-dimensional (2D) Sn−Pb mixed-halide perovskite compound by converting a SnCl 2 /PbCl 2 precursor in a phenylethylamine iodide (PEAI) atmosphere from 80 to 120 °C. A conversion temperature of 100 °C is optimal for the growth of a highly crystalline, uniform, and compact 2D Pb−Sn compound perovskite layer with well-defined grains up to 5 μm, consistent with its optical absorbance and emission properties. Simultaneously, a crystalline PbI 2 layer is produced and attributed to the interruption of the intercalation process. Temperature-dependent photoluminescence measurements show a single excitonic peak from 20 to 360 K for both 2D Sn-only and Sn−Pb compound films, highlighting the phase stability of the material. The observed excitonic peak broadening in the compound film is attributed to growth in the defect density accompanied by a weakening of the exciton−phonon interaction caused by Frenkel-like excitons. This work will contribute toward an understanding of the transport properties of CVDgrown 2D perovskites that will develop the capability of producing 2D-layered field-effect transistors and solar cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.