Due to the biotoxicity and environmental contamination, electronic products containing cadmium are strictly limited. [1][2][3][4] Therefore, the development of environmental-friendly cadmium-free quantum dots (QDs) with competitive performance is one of the frontiers of current QD researches. [5,6] InP QD is considered as the most promising alternative in cadmiumfree QD due to its large exciton Bohr radius and stability. [7][8][9] At present, the performance of red and green InP QDs and devices has been greatly improved. The photoluminescence quantum yield (PLQY) of red InP QDs reached 100%, and the external quantum efficiency (EQE) of red InP quantum dot light-emitting diode (QLED) was 21%. [10] For green light-emitting InP QDs, the QY reached 95% with a QLED EQE of 7.06%. [11] However, the highest QY of blue InP QDs was only 82% and the corresponding QLED EQE was only 2.5%. [12] Thus, the synthesis of high-QY blue InP QDs is of great significance.At present, only a few types of alkylphosphine can be used to synthesize InP QDs due to the difficulty of meeting both the high reactivity and stability of most phosphorus precursors. In earlier studies, the more reactive tri(trimethylsilyl) phosphine [(TMS) 3 P] was used as the precursor of phosphorus. [13,14] Although QDs with good emission performance can be obtained, (TMS) 3 P is expensive and produces highly toxic phosphine gas when exposed to air. In 2016, Tessier et al. [15] proposed a synthesis scheme using indium halide and tri(dimethylamine)phosphine [(DMA) 3 P] as precursors, achieving an economic and large-scale synthesis of InP QDs. By using different halogens, the size of the InP QDs can be controlled, resulting in different emission wavelengths. Also, compared to (TMS) 3 P, (DMA) 3 P is more stable and does not produce toxic gases when exposed to air. Due to its low toxicity and high stability, and its price is only 1/80 times that of (TMS) 3 P, the selection of (DMA) 3 P as the phosphorus precursor to synthesize InP QDs is becoming a promising direction in the future. [16] The lower QY of blue InP QDs is mainly caused by two reasons. First, the small size of blue InP leads to its large specific surface area, and oxidation of the InP surface by water and Red and green InP quantum dots (QDs) already have been demonstrated with excellent luminescence performance closing the gap with CdSe-based QDs. However, the performance of blue InP QDs still lags behind that of red and green QDs. For blue InP QDs synthesized by aminophosphine and zinc iodide, the inherent Ipossesses weak passivation ability. By introducing Brwith a smaller ion radius and larger binding energy, the quantum yield of blue InP QDs is increased from 54% to 93%, which is the highest value reported so far. Meanwhile, the long-chain 1-dodecanethiol is replaced by the short-chain 1-octanethiol through ligand exchange to increase the carrier injection efficiency. The blue quantum dot light-emitting diodes (QLEDs) made of these QDs showed an external quantum efficiency of 2.6%, which is notably th...

The unbalanced carrier injection is a key factor that deteriorates the performance of blue InP quantum dot light-emitting diodes (QLEDs). Therefore, to achieve efficient blue InP QLEDs, an effective strategy that balances carrier injection through enhancing the hole injection and transport is in demand. In this study, we introduced an ultrathin MoO3 electric dipole layer between the hole injection layer and the hole transport layer (HTL) to form a pair of dipole-induced built-in electric fields with forward resultant direction to enhance hole injection and facilitate the balance of carrier injection. Meanwhile, the p-doping effect by MoO3 leads to increased carrier concentration and decreased trap density of interfacial HTL, therefore improved its effective hole mobility. Consequently, the maximal external quantum efficiency of blue InP QLEDs was enhanced from 1.0% to 2.1%. This work provides an effective method to balance carrier injection by modulating hole injection and transport, indicating the feasibility to realize high-efficiency QLEDs.

The excited-state manipulation of the phosphorescent iridium(III) complexes plays a vital role in their photofunctional applications. The development of the molecular design strategy promotes the creative findings of novel iridium(III) complexes. The current molecular design strategies for iridium(III) complexes mainly depend on the selective cyclometalation of the ligands with the iridium(III) ion, which is governed by the steric hindrance of the ligand during the cyclometalation. Herein, a new molecular design strategy (i.e., random cyclometalation strategy) is proposed for the effective excited-state manipulation of phosphorescent cyclometalated iridium(III) complexes. Two series of new and separable methoxyl-functionalized isomeric iridium(III) complexes are accessed by a one-pot synthesis via random cyclometalation, resulting in a dramatic tuning of the phosphorescence peak wavelength (∼57 nm) and electrochemical properties attributed to the high sensitivity of their excited states to the position of the methoxyl group. These iridium(III) complexes show intense phosphorescence ranging from the yellow (567 nm) to the deep-red (634 nm) color with high photoluminescence quantum yields of up to 0.99. Two deep-red emissive iridium(III) complexes with short decay lifetimes are further utilized as triplet emitters to afford efficient solution-processed electroluminescence with reduced efficiency roll-offs.

As an effective manufacturing technology, inkjet printing is very suitable for the fabrication of perovskite light-emitting diodes in next-generation displays. However, the unsatisfied efficiency of perovskite light-emitting diode created with the use of inkjet printing impedes its development for future application. Here, we report highly efficient PeLEDs using inkjet printing, with an external quantum efficiency of 7.9%, a current efficiency of 32.0 cd/A, and the highest luminance of 2465 cd/m2; these values are among the highest values for the current efficiency of inkjet-printed PeLED in the literature. The outstanding performance of our device is due to the coffee-ring-free and uniform perovskite nanocrystal layer on the PVK layer, resulting from vacuum post-treatment and using a suitable ink. Moreover, the surface roughness and thickness of the perovskite layer are effectively controlled by adjusting the spacing of printing dots. This study makes an insightful exploration of the use of inkjet printing in PeLED fabrication, which is one of the most promising ways for future industrial production of PeLEDs.