The photoluminescence stability of all-inorganic perovskite nanocrystals (CsPbBr3) with different size is studied.

It is challenging to improve the emission efficiency of Mn-doped CsPbCl 3 (Mn:CsPbCl 3 ) nanocrystals (NCs) because the excellent optical performances are dependent on high doping efficiency and few defects and traps. Steady-state and timeresolved photoluminescence (PL) spectroscopies were used to investigate the luminescence properties of Mn:CsPbCl 3 NCs with different Mn doping levels synthesized in the presence of nickel chloride. The doping efficiency of Mn ions in Mn:CsPbCl 3 NCs was greatly enhanced in the presence of NiCl 2 , and the PL wavelength of Mn 2+ ions was tuned from 594 to 638 nm by varying the concentration of dopant Mn from 0.11% to 15.25%. The high emission quantum yields of Mn:CsPbCl 3 NCs with orange and red emissions peaked at 600 and 620 nm in hexane were 70% and 39%, respectively. The improvement in doping and emission efficiencies of Mn 2+ was attributed to the enhanced formation energies of the Mn doping under the Mn and Ni codoped configuration and the resulting reduction of defects and traps in Mn:CsPbCl 3 NCs with incorporation of Ni 2+ ions.

Photocarrier recombination dynamics in ternary chalcogenide CuInS2 quantum dots (CIS QDs) was studied by means of femtosecond transient-absorption (TA) and nanosecond time-resolved photoluminescence (PL) spectroscopy. Under strong excitation, the TA dynamics in CIS QDs is well described by a simple rate equation including single-carrier trapping, free-to-bound recombination, and trap-assisted Auger recombination. Under weak excitation, on the other hand, the PL decays of the QDs are composed of a short-lived component caused by surface trapping and a long-lived one caused by free-to-bound recombination. It is found that the surface trapping accelerates markedly with decreasing QD size while the free-to-bound radiative recombination hardly depends on the QD size. Besides this, we observed both a decrease in the PL lifetimes and a dynamic spectral redshift, which are attributed to the surface trapping and the coexistent inhomogeneous broadening in CIS QDs. The spectral redshift becomes less pronounced in CIS/ZnS core/shell QDs because of the suppression of the fast nonradiative recombination caused by the passivation of the surface traps. These results give clear evidence that the free-to-bound model is appropriate for interpreting the optical properties of CIS QDs.

Quantum dot light-emitting diodes (QLEDs) with an excellent external quantum efficiency (EQE) and an excellent lifetime almost meet the requirements for low-brightness displays. However, the short operation lifetime under high brightness limits the application of QLEDs in outdoor displays and lightings. Herein, we report a highly efficient, stable red QLED using co-doped lithium and magnesium as well as a magnesium oxide shell-coated zinc oxide nanoparticle layer as an electron transport layer (ETL). The optimized QLED has a high peak EQE of 20.6%, a low efficiency roll-off at high current, and a remarkably long lifetime T 95 of >11000 h at 1000 cd m −2 , which is an indication of the realization of the most stable red QLED to date. The improvement in the long term stability of the QLED is attributed to the use of a co-doped and shell-coated zinc oxide ETL with a reduced level of electron injection to improve the charge balance in the device.

InP-based quantum dot light-emitting diodes (QLEDs), as less toxic than Cd-free and Pb-free optoelectronic devices, have become the most promising benign alternatives for the next generation lighting and display. However, the development of green-emitting InP-based QLEDs still remains a great challenge to the environmental preparation of InP quantum dots (QDs) and superior device performance. Herein, we reported the highly efficient green-emitting InP-based QLEDs regulated by the inner alloyed shell components. Based on the environmental phosphorus tris(dimethylamino)phosphine ((DMA)3P), we obtained highly efficient InP-based QDs with the narrowest full width at half maximum (~35 nm) and highest quantum yield (~97%) by inserting the gradient inner shell layer ZnSexS1−x without further post-treatment. More importantly, we concretely discussed the effect and physical mechanism of ZnSexS1–x layer on the performance of QDs and QLEDs through the characterization of structure, luminescence, femtosecond transient absorption, and ultraviolet photoelectron spectroscopy. We demonstrated that the insert inner alloyed shell ZnSexS1−x provided bifunctionality, which diminished the interface defects upon balancing the lattice mismatch and tailored the energy levels of InP-based QDs which could promote the balanced carrier injection. The resulting QLEDs applying the InP/ZnSe0.7S0.3/ZnS QDs as an emitter layer exhibited a maximum external quantum efficiency of 15.2% with the electroluminescence peak of 532 nm, which was almost the highest record of InP-based pure green-emitting QLEDs. These results demonstrated the applicability and processability of inner shell component engineering in the preparation of high-quality InP-based QLEDs.

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Zinc-anode-based electrochromic devices (ZECDs) are emerging as the next-generation energy-efficient transparent electronics. We report anatase W-doped TiO2 nanocrystals (NCs) as a Zn2+ active electrochromic material. It demonstrates that the W doping in TiO2 highly reduces the Zn2+ intercalation energy, thus triggering the electrochromism. The prototype ZECDs based on W-doped TiO2 NCs deliver a high optical modulation (66% at 550 nm), fast spectral response times (9/2.7 s at 550 nm for coloration/bleaching), and good electrochemical stability (8.2% optical modulation loss after 1000 cycles).

Controlling the structure of halide perovskites through component engineering, and thus revealing the changes in luminescence properties caused by the conversion of crystal structure, is of great significance. Herein, we report a controllable synthetic strategy of threedimensional (3D) Cs 2 KInCl 6 and zero-dimensional (0D) (Cs/ K) 2 InCl 5 (H 2 O) halide perovskites by changing the Cs/K feed ratio. 3D Cs 2 KInCl 6 double perovskites are obtained at the Cs/K feed ratio of 1:1, while 0D (Cs/K) 2 InCl 5 (H 2 O) perovskites are formed at the Cs/K feed ratio of 2:1. Further, a reversible crystal structure transformation between 3D Cs 2 KInCl 6 double perovskites and 0D (Cs/K) 2 InCl 5 (H 2 O) perovskites can be achieved by subsequent addition of metal-salt precursors. In addition, the emission efficiency of two perovskite structures can be greatly boosted by breaking the forbidden transition through Sb doping, and as a result, a novel green/yellow reversible emission switch is generated. Meanwhile, the relationship between perovskite structure and luminescence mechanism has been systematically revealed. These environmentally stable halide perovskites have great potential to be applied in optoelectronic devices.