Dynamics of exciton–polariton emission in CuI

Abstract

We report on temperature-dependent (10 K – 250 K) spectral and dynamical properties of free exciton–polariton and bound exciton emission in copper iodide (CuI) bulk single crystals analyzed by means of time-resolved photoluminescence spectroscopy. The characteristic line shape of the polariton emission at low temperatures is interpreted in terms of the “k-linear term effect” on the degenerate Z1,2 excitons in CuI. For free exciton–polaritons, an increase in the decay time with increasing temperature up to 360 ps at 160 K is observed. For bound exciton emission, decay times between 180 ps and 380 ps are observed at low temperatures, revealing the expected EB3/2 dependence of radiative lifetime on the localization energy. Based on the observed rise times of bound excitons at low temperatures, a defect density of shallow acceptors of 1 × 1017 cm−3 was estimated, in agreement with measured room temperature free hole density.

Dielectric function of CuBr$_\mathrm{x}$I$_{1-\mathrm{x}}$ alloy thin films

“…In the case of CuI, the calculated quasi-particle gap of 3.07 eV (see Fig. 3 (a)) matches the experimental value under consideration of the exciton binding energy of 62 meV for CuI 25 excellently well. For CuBr, the calculated quasi-particle gap is approximately 2.7 eV (see Fig.…”

“…A full discussion of the influence of the ordered configurations together with other effects one needs to consider is given in the supplementary material. Furthermore, we note that due to the high exciton binding energy of 62 meV for CuI 25 and 108 meV for CuBr 68 , the optical transitions exhibit a strong excitonic character even at room temperature. Thus, since the exciton binding energy is expected to depend on the alloy composition, it is not immediately obvious that the theoretically computed bowing of the bandgap must match the experimentally observed bowing of the E 0 transition.…”

“…The zincblende phase of CuI, γ-CuI, has particularly interesting electronic properties and therefore has been attracting increasing interest 12,19,21,24 . With a bandgap of around 3.1 eV 19,25 , large exciton binding energies of 62 meV 25 and high hole mobilites 26 of µ > 40 cm 2 V −1 s −1 in bulk single crystals, γ-CuI is a suitable transparent ptype material for optoelectronic applications. Until now, the application potential of CuI has already been demonstrated in transparent p-n heterojunctions 27 , thin film transistors 2,28,29 , light-emitting diods 30,31 , perovskite solar cells [32][33][34] , UV-photodetectors 35 and thermoelectric devices 5 .…”

“…Also CuBr x I 1x thin film were successfully applied to build transparent p-n-junctions 44 , solar cells 45,46 and thin film transistors 20 . In contrast of the binary compounds, CuI 25,[47][48][49][50] and CuBr [51][52][53] , only few theoretical and experimental results are reported in literature for CuBr x I 1x alloys 22,39,43,54,55 . Although absorption and reflectivity spectra of CuBr x I 1x were already published in the 60s 54 , a dedicated investigation of the electronic structure and optical properties as a function of alloy composition is still lacking.…”

Epitaxial Growth of AgxCu1−xI on Al2O3(0001)

“…In the search for suitable transparent p ‐type semiconductors, copper iodide (CuI) in particular has become the focus of current research. With its large bandgap of 3.1 eV, [ 1,2 ] high exciton binding energy of , [ 2,3 ] and high hole mobility up to [ 4 ] , CuI is ideally suited for future applications in transparent transistors, [ 5,6 ] solar cells, [ 7,8 ] and photodetectors. [ 9 ] Recently, various approaches have also been discussed to modify the electrical and optical properties of CuI using alloys, such as [ 10–12 ] .…”