On the Interpretation of Luminescence of Lead Halide Crystals

Abstract

Emission and excitation spectra, and the luminescence decay kinetics have been studied for PbCl 2 crystals at the temperatures 0.45-100 K. It has been found that even at the lowest temperatures, where the non-radiative decay of exciton states in PbCl 2 does not take place, the decay times of both the ultraviolet (UV) and the blue (B) exciton emission are by a few orders of magnitude shorter than the decay times of the emission arising from the triplet relaxed excited state of Pb 2þ centres in lead-doped ionic crystals. A conclusion has been drawn that the luminescence of lead halides cannot be connected with single Pb 2þ ions. It is proposed that the radiative decay of the self-trapped excitons of the type of {(Pb 2 ) 3þ þ hole} is responsible for the UV and the B emission of PbCl 2 crystals, while the lowest-energy (BG) emission arises from the tunnelling recombinations between the (Pb 2 ) 3þ -type self-trapped electrons and V K -type self-trapped holes.

Polaron self-localization in white-light emitting hybrid perovskites

“…This splitting is characteristic of a vibronic progression and indicates strong electronphonon coupling induced by confinement within the inorganic wells. A similar splitting was also found in PbCl2 and PbBr2, 26 where charge self-trapping has been previously observed, and suggests a correlation with the corresponding inorganic precursors. The narrower spectral linewidth of the vibronic replicas in (EDBE)PbCl4 is consistent with its ordered planar structure, compared to the corrugated structure of (EDBE)PbBr4 (see Fig.…”

“…42,44 Similarly, charge self-trapping at low temperature in lead halides PbX2 (X=Cl, Br) is known to yield large Stokes shift and broad photoluminescence. 26,[45][46][47] In this case, electron-spin resonance (ESR) measurements have also identified the self-trapping centers to be Pb2 3+ for STEL, and Pb 3+ and X2 -(X=Cl, Br) for STH. 42,45,[47][48][49][50][51][52] The latter, also known as Vk centers, 53,54 are commonly observed in alkali halides, 44 where hole trapping strengthens the interaction between halide pairs leading to the formation of dimer species X2within the ionic crystal.…”

“…The excitation energy is resonant to the excitonic peak of the perovskite, Eexc = 3.76 eV and Eexc=3. 26…”

Thermomechanical Measurements of Lead Halide Single Crystals

“…The physical properties of lead halides PbX 2 (X ¼ Cl, Br, I) have been extensively studied for many years with an increasing interest in their luminescent properties [1,2], and their possible applications in acousto-optical devices [3] and as radiation detectors [4]. For these reasons much attention has been paid to the growth of lead halide crystals.…”

Exciton-relaxation dynamics in lead halides

“…The PL components have been assigned to STE lumines-PL Intensity (arb. units) cence by many researchers [1,12,19,20,21,22,23]. However, the stable range disagrees with that of self-trapped states in each crystal: In cubic PbF 2 , the PL component at 4 eV is quenched around 30 K [1,21] while the STHs are bleached around 175 K [18].…”