Probing Exciton Move and Localization in Solution-Grown Colloidal CdSe_xS_1–x Alloyed Nanowires by Temperature- and Time-Resolved Spectroscopy

Abstract

Colloidal semiconductor nanowires are interesting materials with polarized optical feature for optoelectronics devices. Previously, we observed an interesting photoluminescence enhancement in colloidal alloyed CdSe x S 1−x nanowires. In the present work, low temperature steady-state and time-resolved photoluminescence spectra were applied to understand the photoluminescence enhancement in these CdSe x S 1−x alloyed nanowires. The band-edge emission and surface-defect emission of alloyed CdSe x S 1−x nanowires, observed in low temperature photoluminescence spectra, show different changing trend with the variation of their composition. Moreover, the radiative lifetime for band-edge emission and surface-defect emission reveals an opposite changing trend with the variation of temperature. These findings suggest that the variation of photoluminescence quantum yields with composition is determined by the competition between exciton move and localization. If the carriers are localized in the interior of nanowires, the migration of photoinduced excitons to their surface will be prohibited, and more probability for radiative recombination at band edge occurred.

Spin-Related Micro-Photoluminescence in Fe3+ Doped ZnSe Nanoribbons

“…The inset of Figure 5b shows the fitted results of PL lifetimes at 300 K. With the temperature increasing, the lifetime decreases from 1.1 to 0.67 ns, which is mostly due to the strong coupling between exciton and acoustic phonons. In particular, the lifetime has a sharp reduction when the temperature lowers than 60 K, which is different from that previously reported [40]. The magnetic phase transition in Fe doped ZnSe nanoribbon may be one cause.…”

Template-Free Synthesis of High-Yield Fe-Doped Cesium Lead Halide Perovskite Ultralong Microwires with Enhanced Two-Photon Absorption

“…For example, the PL peak of one sample is centered at ∼514 nm at room temperature, its peak red shifts to 520 nm at 80 K, which can be ascribed to more population of singlet emission at low temperature, and the mainline of the emission band changes monotonically with temperature at the beginning and tends to be stable at low temperature (Figure b). This red shift of the emission peak with decreasing temperature has also been found in CsPbBr 3 and CsPbI 3 nanowires, which have been attributed to the acoustic phonon–exciton interaction. , More temperature-related PL spectra of the Fe-doped microrod can be found in the Supporting Information (Figure S6), and there is always a clear and small shoulder on the right side of the PL mainline, which should be the singlet components but not the strong electron–phonon coupling in Fe-doped MWs with two dominant modes at 148 and 306 cm –1 . The small shoulder peak should be the lower singlet level in the perovskite .…”

“…This red shift of the emission peak with decreasing temperature has also been found in CsPbBr 3 and CsPbI 3 nanowires, 25 which have been attributed to the acoustic phonon−exciton interaction. 25,49 More temperature-related PL spectra of the Fedoped microrod can be found in the Supporting Information (Figure S6), and there is always a clear and small shoulder on the right side of the PL mainline, which should be the singlet components but not the strong electron−phonon coupling in Fe-doped MWs with two dominant modes at 148 and 306 cm −1 . The small shoulder peak should be the lower singlet level in the perovskite.…”

Multi‐Dimensional Quantum Nanostructures with Polarization Properties for Display Applications

“…To get highly luminescent colloidal semiconductor NWs with attractive polarized light absorption and emissions, Yang and co-workers developed a solution-liquid-solid (SLS) alloy-ing synthetic method, and produced highly luminescent CdSe x S 1À x alloyed NWs (Figure 5b). [23] Commonly, it is hard to fabricate SeÀ S based homogeneous alloy structure, because it requires to balance the different reactivity of the precursors. They think there were two main reasons for the successful homogeneous alloying process.…”