All-inorganic cesium lead halide (CsPbBr3) perovskite quantum dots (QDs), as one kind of promising materials, have attracted considerable attention in optoelectronic applications. Herein, we synthesized the colloidal CsPbBr3 QDs with tunable photoluminescence (PL) (493–531 nm) by adjusting the reaction temperatures, which revealed narrow emission bandwidths of about 25 nm. The average diameters of the QDs could be adjusted from 7.1 to 12.3 nm as the temperature increased from 100 °C to 180 °C. Moreover, the radiative lifetimes of CsPbBr3 QDs were measured to be ~ 2 ns, and the single QD fluorescence intensity time trace results demonstrated its suppressed blinking emission. Moreover, green light emitting diodes by using CsPbBr3 QDs casted on blue LED chips were further fabricated, which provided potential applications in the field of display and lighting technology.The graphical abstract shows photoluminescence spectra of CsPbBr3 quantum dots and one typical light emitting diodes device (inset: schematic diagram and optical image).Download high-res image (264KB)Download full-size image

•Efficient reduction of large voids or pinholes in CsPbBr3 films using ZnO NPs.•CsPbBr3:ZnO films exhibit improved PL intensity and prolonged lifetime.•ASE emission efficiency and ASE threshold of CsPbBr3:ZnO films are improved.Inorganic cesium lead halide perovskites (CsPbX3, X = Cl, Br, I) have attracted enormous attention as a novel optoelectronic material with enhanced stability. However, the perovskite CsPbX3 thin films fabricated by one-step spin-coating method contain the defects of voids or pinholes, seriously affecting their amplified spontaneous emission (ASE) or lasing performance. To solve this issue, herein, we demonstrate that by simply introducing ZnO nanoparticles (NPs) into the CsPbBr3 precursor solution, the CsPbBr3:ZnO films synthesized by one-step spin-coating method exhibit enhanced crystallization, improved photoluminescence (PL) intensity and prolonged lifetime. Introducing the ZnO NPs can provide an effective route for CsPbBr3 nucleation during the spin-coating and annealing process, contributing to compact and smooth thin films with no obviously large voids or pinholes. Under the one-photon (400 nm) and two-photon (800 nm) femtosecond laser excitation, the ASE of CsPbBr3 and CsPbBr3:ZnO films have been investigated at room temperature, respectively. After the film compactness, surface smoothness and crystal size are modified by the ZnO additive, both the emission efficiency and the ASE threshold of the CsPbBr3:ZnO films have been improved in comparison with the pure CsPbBr3 films.Download high-res image (320KB)Download full-size image

AbstractHalide perovskite nanomaterials have recently attracted a lot of attention in the nanoscale laser research field, especially two-photon pumped lasing in halide perovskite nanomaterials has been considered as an ideal alternative strategy to achieve frequency upconversion. However, the poor stability of current organic–inorganic lead halide perovskite materials hinder their further practical applications. Herein, facile solution-processed cesium lead halide perovskite CsPbX3 (X = Br, I, or Cl) microcubes with low-threshold lasing, high quality, enhanced stability, and excellent wavelength tunability are reported. These as-prepared CsPbX3 microcubes display excellent structure stability under ambient conditions for several months and they are found to be more robust than their organic–inorganic counterparts. The smooth end facets and wavelength-comparable dimensions make these microcubes promising for high-quality laser cavities in three dimensions. Fabry–Perot lasing is demonstrated in CsPbX3 microcubes, the process of which is investigated by dynamic emission. In addition, tunable amplified spontaneous emission is achieved with low threshold under both one- and two-photon excitation, which can maintain a stable emission for over 10 hours under continuous intense laser shots in ambient atmosphere. The findings suggest that solution-processed all-inorganic perovskite microcubes can be used as excellent gain medium for frequency upconversion lasers, which would offer a new platform for nonlinear photoelectric devices.

•All-inorganic CsPbX3 for low-threshold and wavelength-tunable laser application.•CsPbX3 QD with tunable photoluminescence (400–700 nm) through adjusting different compositions.•CsPbX3 QD showed relatively strong photon antibunching property.Recent reports regarding metal halide semiconductors of perovskite nanocrystal structures have presented us a promising future on their optoelectronic applications such as laser and light harvesting devices. In this paper, all-inorganic perovskites CsPbX3 (X=Cl, Br and I) quantum dots (QDs) with tunable fluorescence from 400 nm to 700 nm were prepared by a facile hot-injection method. Besides, random lasing with coherent feedback was observed in films of CsPbX3 QDs. Under 400 nm optical excitation at room temperature, sharp lasing peaks emission at around 427 nm, 527 nm and 539 nm with low pump thresholds intensity were achieved by halide substitution. The dynamic fluorescence from one single quantum dot also was detailed investigated. These results demonstrated that all-inorganic perovskites could be used as low-threshold and wavelength-tunable gain materials for lasing application at room-temperature.All-inorganic perovskites CsPbX3 (X=Cl, Br and I) quantum dots (QDs) with tunable fluorescence from 400 nm to 700 nm were prepared by a facile hot-injection method. At room temperature, sharp random lasing peaks emission around 427 nm, 527 nm and 539 nm with low pump thresholds intensity were achieved by halide substitution.

The excitonic relaxation and coherent vibrational dynamics in stairlike zinc chlorin aggregates prepared for mimicking chlorosome in nature have been studied simultaneously by 6.8 fs real-time vibrational laser spectroscopy. The relaxation from Q-exciton state to the dark nonfluorescent charge-transfer (CT) state is determined to be 850 ± 70 fs. The spectral distribution of the molecular vibrational amplitude has been discussed in terms of the difference in the equilibrium positions of potential curves between the ground state and the excited state. Since the displacement in the coordinate space from the potential minimum of the ground state to that of the excited states is small, coherent oscillations generated by the impulsive excitation are strongest where the slope of the excitonic resonance is largest. Consequently, the probe wavelength dependence of the amplitude modulation follows the first derivative of the excitonic resonance, and π phase jump has been observed. Excitonic transition energy modulation caused by the coherent molecular vibrations has also been studied, and the vibrational mode with a low frequency of 146 cm–1 is found to play a dominating role in the transition energy shift effect.

•Electronic dephasing time in MEH-PPV is determined as 25 ± 2 fs using a sub 7 fs pulse.•Self-trapping time of a free exciton to form a polaron is measure as 50 ± 23 fs.•Mechanism of real-time dynamic mode-coupling among vibration modes is clarified.•Energy ladder descent process in vibration modes is clarified by a moment method.The electronic population decay time is determined to be about 500 fs in (poly-[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylenevinylene] (MEH-PPV) using 5.7 fs pulses. The ultrafast electronic dephasing time and the self-trapping time of free exciton to form an exciton polaron is determined as 25 ± 2 fs and 50 ± 23 fs, respectively. Real-time spectrogram analysis reveals dynamic mode coupling among the high-frequency and low-frequency modes. The energy-ladder descent vibrational process is clarified using the first moment of the difference absorption spectrum. The phase relaxation time is calculated from the widths of the Fourier spectra of several strongly coupled modes.

•Combination of sub-5-fs laser and broadband multi-channel lock-in detector.•Real-time vibration spectra in a broad electronic spectral range.•Potential hypersurface via Huang–Rhys factors determined for multi-modes.Real-time vibrational spectra in a polyacetylene derivative, poly[o-TFMPA([o-(trifluoromethyl) phenyl]acetylene)] in a broad electronic spectral region were observed using a sub-7-fs laser. Using the frequencies and initial phases of vibrational modes obtained by the spectroscopy, the assignment of the wavepackets was made. From the first moment, Huang–Rhys parameters were determined for six most prominent modes, which characterize the potential hypersurface composed of multi-dimensional vibrational mode spaces.