Through introducing a probe layer of bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium (FIrpic) between QD emission layer and 4, 4-N, N- dicarbazole-biphenyl (CBP) hole transport layer, we successfully demonstrate that the electroluminescence (EL) mechanism of the inverted quantum dot light-emitting diodes (QD-LEDs) with a ZnO nanoparticle electron injection/transport layer should be direct charge-injection from charge transport layers into the QDs. Further, the EL from QD-LEDs at sub-bandgap drive voltages is achieved, which is in contrast to the general device in which the turn-on voltage is generally equal to or greater than its bandgap voltage (the bandgap energy divided by the electron charge). This sub-bandgap EL is attributed to the Auger-assisted energy up-conversion hole-injection process at the QDs/organic interface. The high energy holes induced by Auger-assisted processes can be injected into the QDs at sub-bandgap applied voltages. These results are of important significance to deeply understand the EL mechanism in QD-LEDs and to further improve device performance.

All-inorganic CsPbX ₃ (X = Cl, Br, I) perovskite quantum dots (QDs) have become a kind of optoelectronic material with huge application prospects due to their excellent physical and optical properties.

Efficient transparent quantum-dot light emitting diodes (QD-LEDs) are demonstrated by using a silver nanowire (AgNW) cathode. The devices are fabricated through a solution technique, not any vacuum processes are involved. Almost identical performance is obtained for both sides of the transparent device, which is primary due to the high transmittance of AgNW cathode. The maximum luminance (efficiency) for ITO and AgNW side is 25,040 cd/m² (5.6 cd/A) and 23,440 cd/m² (5.2 cd/A), respectively. The average specular transmittance of the device (involving the glass substrate) is over 60% in the visible range. This study indicates that AgNW electrodes can serve as a cost-effective, flexible alternative to ITO and thereby improve the economic viability and mechanical stability of QD-LEDs. All the results suggest that this is an important progress toward producing transparent QD-LEDs based displays and lighting sources.

The structure transformation from CsPbBr ₃ to Cs ₄ PbBr ₆ perovskite nanocrystals induced fluorescence enhancement was detected and applied in the LED devices.

The facile one-pot synthesis of NaYF₄ :Yb, Ln/NaYF₄ :Yb core/shell (CS) upconversion nanoparticles (UCNPs) was firstly developed through the successive ion layer adsorption and reaction (SILAR) technique, which represents an attractive alternative to conventional synthesis utilizing the chloride of Ln as the precursors, where the Ln doped NaYF₄ core was firstly purified and then an epitaxial shell of the desired thickness was obtained by the injection of shell precursors to a solution of the purified NaYF₄ core. The temperature-dependent shell growth mechanism and upconversion luminescent properties were explored thoroughly. A temperature of 280 °C proved to be the optimal shell growth temperature to prepare the compact CS structure with the highest luminescent enhanced efficiency for this preparative system. The shell thickness could be easily tuned using this SILAR technique from about 3 monolayers (ML) to 44 ML. The UC luminescent intensity was found to be increased with increasing shell thickness, and at last the effect of surface on the PL could be completely excluded by an appropriate shell thickness. Furthermore, the performance of the SILAR technique was also demonstrated by comparing Tm³⁺ and Er³⁺ doped separately in the core and shell with the Ln ions co-doped in the core.