Large-Area Nanocrystalline Caesium Lead Chloride Thin Films: A Focus on the Exciton Recombination Dynamics

Abstract

Caesium lead halide perovskites were recently demonstrated to be a relevant class of semiconductors for photonics and optoelectronics. Unlike CsPbBr3 and CsPbI3, the realization of high-quality thin films of CsPbCl3, particularly interesting for highly efficient white LEDs when coupled to converting phosphors, is still a very demanding task. In this work we report the first successful deposition of nanocrystalline CsPbCl3 thin films (70–150 nm) by radio frequency magnetron sputtering on large-area substrates. We present a detailed investigation of the optical properties by high resolution photoluminescence (PL) spectroscopy, resolved in time and space in the range 10–300 K, providing quantitative information concerning carriers and excitons recombination dynamics. The PL is characterized by a limited inhomogeneous broadening (~15 meV at 10 K) and its origin is discussed from detailed analysis with investigations at the micro-scale. The samples, obtained without any post-growth treatment, show a homogeneous PL emission in spectrum and intensity on large sample areas (several cm2). Temperature dependent and time-resolved PL spectra elucidate the role of carrier trapping in determining the PL quenching up to room temperature. Our results open the route for the realization of large-area inorganic halide perovskite films for photonic and optoelectronic devices.

Ultra-fast low temperature scintillation and X-ray luminescence of CsPbCl3 crystals

“…The narrow peak 1 is manifest only at low temperatures and its position in energy at 2.97 eV is very close to the low-temperature exciton absorption of CsPbCl 3 . The position of this peak agrees with the published data on photoluminescence of bulk crystals, 19,20,35 microcrystals and films, 36,37 of CsPbCl 3 . It should be noted, however, that in nanocrystals this peak is shifted towards higher energy, 38,39 similar to what is observed in other inorganic halide perovskites.…”

Electrical and Optical Characterization of CsPbCl3 Films around the High-Temperature Phase Transitions

“…However, the low-temperature values for the band gap energy below 300 K in ref. [ 27 ] are strongly different with all the rest of published experimental results ([ 12 ] and refs therein). The red shift reported in Figure 6 a–c highlights a change in the band gap energy, which is possibly related to the phase transitions that are reported for CsPbCl 3 in the T range (300–330 K) [ 13 , 14 , 15 , 16 ].…”

“…The dynamic working pressure was 2 × 10 −6 atm and the deposition rate was between 5 and 7 × 10 −2 nms −1 . The samples were fully characterized concerning morphology, structure, and stoichiometry, as extensively described in [ 12 , 18 , 19 ].…”

“…Recently, CsPbCl 3 with a band gap ≈ 3 eV at 300 K has driven a lot of attention for the realization of efficient light emitters in the blue spectral range, instead of GaN and AlGaN and, in combination with a converting phosphor, for white LEDs [ 11 ]. Unlike other inorganic lead halide perovskites, which are commonly realized by solution-based techniques, CsPbCl 3 synthesis is more difficult; it has been recently reported that vapor phase deposition, in particular RF magnetron sputtering, allows for the deposition of nanometric films with a good degree of homogeneity on a large scale and state of the art optical quality [ 12 , 13 ]. A common feature of CsPbX 3 perovskites is the presence of structural phase transitions from the low symmetry lattice (monoclinic) at low temperature to the high symmetric lattice (cubic) at high temperature (T).…”

Evaporation of Methylammonium Iodide in Thermal Deposition of MAPbI3

“…Yan et al reported that the grain size of MAPbBr 3 thin film can be modified by changing the molar ratio of the organic to inorganic precursor, and PL emissions can reach their maximum when the molar ratio is two [30]. Falsini et al showed that there are two PL emissions in CsPbCl 3 thin film, and these emissions are attributed to the different morphologies of the crystallites [31].…”