Transient Spectroscopy of Glass-Embedded Perovskite Quantum Dots: Novel Structures in an Old Wrapping

Abstract

Semiconductor doped glasses had been used by the research and engineering communities as color filters or saturable absorbers well before it was realized that their optical properties were defined by tiny specs of semiconductor matter known presently as quantum dots (QDs). Nowadays, the preferred type of QD samples are colloidal particles typically fabricated via organometallic chemical routines that allow for exquisite control of QD morphology, composition and surface properties. However, there is still a number of applications that would benefit from the availability of high-quality glassbased QD samples. These prospective applications include fiber optics, optically pumped lasers and amplifiers, and luminescent solar concentrators (LSCs). In addition to being perfect optical materials, glass matrices could help enhance stability of QDs by isolating them from the environment and improving heat exchange with the outside medium. Here we conduct optical studies of a new type of all-inorganic CsPbBr 3 perovskite QDs fabricated directly in glasses by hightemperature precipitation. These samples are virtually scattering free and exhibit excellent waveguiding properties which makes them well suited for applications in, for example, fiber optics and LSCs. However, the presently existing problem is their fairly low room-temperature emission quantum yields of only ca. 1 -2%. Here we investigate the reasons underlying the limited emissivity of these samples by conducting transient photoluminescence (PL) and absorption measurements across a range of temperatures from 20 -300 K. We observe that the low-temperature PL quantum yield of these samples can be as high as ~25%. However, it quickly drops (in a nearly linear fashion) with increasing temperature. Interestingly, contrary to traditional thermal quenching models, experimental observations cannot be explained in terms of a thermally activated nonradiative rate but rather suggest the existence of two distinct QD sub-ensembles of "emissive" and completely "nonemissive" particles. The temperature-induced variation in the PL efficiency is likely due to a structural transformation of the QD surfaces or interior leading to formation of extremely fast trapping sites or nonemissive phases resulting in conversion of emissive QDs into nonemissive. Thus, future efforts on improving emissivity of glass-based perovskite QD samples might focus on approaches for extending the range of stability of the low-temperature up to room temperature.

Revealing the Effects of Defects on Ultrafast Carrier Dynamics of CsPbI3 Nanocrystals in Glass

“…At higher pump intensities, multiple excitons can be generated. By subtracting the relaxation process of single exciton using the previously reported method, , the biexciton lifetimes of CsPbI 3 NCs in different specimens are fitted (Figure S6). The results show that the biexciton lifetime increases from 9.9 ± 0.5 ps (HT47012, Figure S6a) to 25.1 ± 0.8 ps (HT48010, Figure S6b), 19.8 ± 0.4 ps (HT48012, Figure S6c), 51.2 ± 3.7 ps (HT49010, Figure S6d), and 83.9 ± 4.4 ps (HT50010, Figure S6e).…”

“…The charge carrier transport performance at the interface of perovskite solar cells has also been studied using time-resolved spectroscopy. , However, besides some research on conventional CdS x Se 1– x and PbS NC-doped glasses, − the ultrafast charge carrier dynamics of CsPbX 3 NCs embedded in glasses has rarely been reported. Recently, Klimov et al investigated the temperature-dependent time-resolved fluorescence dynamics of CsPbBr 3 NC-doped glasses and confirmed that the biexciton lifetime of CsPbBr 3 NCs was consistent with the colloidal NCs . However, the effects of glass composition/thermal annealing conditions on the charge carrier dynamics of CsPbX 3 NCs remain largely elusive, and understanding of these effects on the carrier kinetics is full of significance to develop the photoelectric device with high stability.…”

“…30 The charge carrier transport performance at the interface of perovskite solar cells has also been studied using time-resolved spectroscopy. 31,32 However, besides some research on conventional CdS x Se 1−x and PbS NC-doped glasses, 33−35 36 However, the effects of glass composition/ thermal annealing conditions on the charge carrier dynamics of CsPbX 3 NCs remain largely elusive, and understanding of these effects on the carrier kinetics is full of significance to develop the photoelectric device with high stability.…”

Mid-Infrared Luminescence of the High Stability Perovskite CsPb1–xErxBr3-ZrF4-BaF2-LaF3-AlF3-NaF Fluoride Glass

“…When the temperature changes from 300 to 20 K, the fluorescence quantum yield of the CsPbBr 3 perovskite becomes larger. 15 The CsPbBr 3 perovskite is implanted into B 2 O 3 −SiO 2 −ZnO oxide glass to improve its thermal stability. After eight thermal cycles between 293 and 413 K, the photoluminescence (PL) intensity did not change.…”

“…The CsPbBr 3 perovskite is embedded in the silicate glass matrix to improve its temperature stability. When the temperature changes from 300 to 20 K, the fluorescence quantum yield of the CsPbBr 3 perovskite becomes larger . The CsPbBr 3 perovskite is implanted into B 2 O 3 –SiO 2 –ZnO oxide glass to improve its thermal stability.…”