The exciton relaxation process of CsPbI₃ perovskite nanocrystals (NCs) has been investigated by using transient absorption (TA) spectroscopy. The hot exciton relaxation process is confirmed to exist in the CsPbI₃ NCs, through comparing the TA data of CsPbI₃ NCs in low and high energy excitonic states. In addition, the Auger recombination and intrinsic decay paths also participate in the relaxation process of CsPbI₃ NCs, even the number of exciton per NC is estimated to be less than 1. Excitation intensity-dependent TA data further confirms the existence of Auger recombination. Meanwhile, the spectral data also confirms that the weight of hot exciton also increase together with that of Auger recombination at high excitation intensity when CsPbI₃ NCs in high energy excitonic states.

ZnO nanoparticles (NPs) play a crucial role in advancing quantum-dot light-emitting diodes (QLEDs) because of their excellent electron transport properties. While the conductivity of ZnO is determined by both the density and mobility of charge carriers, a previously overlooked problem is that excessive carrier density in ZnO can lead to nonradiative Auger recombination at the quantum-dot/ZnO interface. An ideal electron transport layer should possess both high mobility and low carrier density. Here, we achieve such transport properties in ZnO NP films through operando recrystallization, a process triggered by the diffusion of Al ions from the cathode under acidic conditions. This diffusion induces the coalescence of neighboring ZnO NPs, forming defect-passivated, long-range ZnO crystals. When used as the electron transport layer in QLEDs, recrystallized ZnO NPs enhance the external quantum efficiency from 17.2% to 33.7% compared with devices with conventional ZnO electron transport layers. These findings offer valuable insights into the development of charge transport materials for high-performance optoelectronic devices.

The interactions between QDs and s-NiO can be largely suppressed through introducing a ultrathin Al₂O₃passivating layer. This highest current efficiency (external quantum efficiency) of 34.1 cd A⁻¹(8.1%) is achieved.

Flexible quantum dot light emitting diodes (QLEDs) are highly desired due to their advantages of foldability, lightweight, and potential applications in lighting and displays. In this report, we successfully fabricated high performance red (R), green (G), and blue (B) three primary color QLEDs based on a poly(ethylene-terephthalate)/ITO/Ag/ITO (PET–IAI) cathode. The multilayer flexible IAI electrode shows outstanding stability even after bending over 2000 times with a critical bending radius of 5 mm; the sheet resistance of the IAI film only increases from 12.7 to 14.8 Ω □⁻¹. The maximum current efficiencies are 16.3, 86.5, and 16.1 cd A⁻¹ for RGB QLEDs, respectively, which is the best device performance for flexible RGB QLEDs reported to date. Moreover, to the best of our knowledge, these are also record efficiencies for the green and blue devices in all the reported QLEDs. Furthermore, all the devices show saturated electroluminescence (EL) with the corresponding emission peaks at 606, 530, and 478 nm for three primary color QLEDs. The superior performance is a result of high transmittance and stability of the PET–IAI film. These results signify remarkable progress in flexible QLEDs and suggest that the PET–IAI based flexible QLEDs can offer a practicable platform for foldable applications.