Colloidal quantum dots (QDs) stand at the forefront of a variety of photonic applications given their narrow spectral bandwidth and near-unity luminescence e ciency. Integrating desired forms of QD lms into photonic systems without compromising their optical or transport characteristics is the key to bridging the gap between expectations and outcomes. Here, we devise a dual-ligand passivation system comprising photocrosslinkable ligands and dispersing ligands to enable QDs to be universally compatible with solution-based patterning techniques. The successful control on the structure of both ligands allows multiscale, direct patterning of the dual-ligand QDs on various substrates via commercialized photolithography (i-line) or inkjet printing systems without compromising the optical properties of QDs or the optoelectronic performances of the devices implementing them. Our approach offers a versatile way of creating various structures of luminescent QDs in a cost-effective and non-destructive manner, and thus enables the implementation of QDs in a range of photonic applications. MainColloidal quantum dots (QDs) are promising materials for use in next-generation light sources due to their wide-ranging bandgap tunability, narrow spectral bandwidths, and near-unity luminescence quantum yields (QY) [1][2][3][4][5] . Together with the capability of cost-effective solution processing, QDs have become the key light-emissive materials for information displays 3,5−7 . The patterned QD down-conversion layer on blue light-emitting diodes (LEDs) renders high-color reproduction and ultra-high image quality in full-color displays 8,9 . Likewise, a laterally patterned array consisting of red, green, and blue (RGB) QD-LEDs, in which QDs convert electrically pumped charge carriers into photons, allows for excellent color gamut and brightness as well as light-weight, thin, and exible form factors [10][11][12][13] , which are suited for wearable neareye displays for virtual reality (VR) and augmented reality (AR) devices. For these "mixed-reality" applications, the QD deposition process should enable the patterning of RGB QDs (or RG QDs along with the bank) into a few micrometer sub-pixels over a large area with high-precision and high-delity 14,15 . At the same time, the process should not disrupt the optical and transport characteristics of QDs and adjacent functional layers. Moreover, from a practical standpoint, it poses great bene t if one can use equipment that are already deployed in display device manufacturing steps for the patterning process.

Electroluminescence from quantum dots (QDs) is a suitable photon source for futuristic displays offering hyper‐realistic images with free‐form factors. Accordingly, a nondestructive and scalable process capable of rendering multicolored QD patterns on a scale of several micrometers needs to be established. Here, nondestructive direct photopatterning for heavy‐metal‐free QDs is reported using branched light‐driven ligand crosslinkers (LiXers) containing multiple azide units. The branched LiXers effectively interlock QD films via photo‐crosslinking native aliphatic QD surface ligands without compromising the intrinsic optoelectronic properties of QDs. Using branched LiXers with six sterically engineered azide units, RGB QD patterns are achieved on the micrometer scale. The photo‐crosslinking process does not affect the photoluminescence and electroluminescence characteristics of QDs and extends the device lifetime. This nondestructive method can be readily adapted to industrial processes and make an immediate impact on display technologies, as it uses widely available photolithography facilities and high‐quality heavy‐metal‐free QDs with aliphatic ligands.

Colloidal Ag(In,Ga)S2 nanocrystals (AIGS NCs) with the band gap tunability by their size and composition within visible range have garnered surging interest. High absorption cross-section and narrow emission linewidth of AIGS NCs make them ideally suited to address the challenges of Cd-free NCs in wide-ranging photonic applications. However, AIGS NCs have shown relatively underwhelming photoluminescence quantum yield (PL QY) to date, primarily because coherent heteroepitaxy has not been realized. Here, we report the heteroepitaxy for AIGS-AgGaS2 (AIGS-AGS) core-shell NCs bearing near-unity PL QYs in almost full visible range (460 to 620 nm) and enhanced photochemical stability. Key to the successful growth of AIGS-AGS NCs is the use of the Ag-S-Ga(OA)2 complex, which complements the reactivities among cations for both homogeneous AIGS cores in various compositions and uniform AGS shell growth. The heteroepitaxy between AIGS and AGS results in the Type I heterojunction that effectively confines charge carriers within the emissive core without optically active interfacial defects. AIGS-AGS NCs show higher extinction coefficient and narrower spectral linewidth compared to state-of-the-art heavy metal-free NCs, prompting their immediate use in practicable applications including displays and luminescent solar concentrators (LSCs).

Auger recombination (AR), whereby the electron−hole recombination energy is transferred to a third charge carrier, prevails in nanocrystal quantum dots (QDs) and governs the performance of QD-based devices including light-emitting diodes and lasers. Thus, precise AR evaluation of QDs is essential for understanding and improving the characteristics of such applications. So far, conventional charging approaches, such as the stir-versus-static method, photochemistry, or electrochemistry, have been able to assess the AR decay rate of either positively (two holes and one electron, X + ) or negatively (one hole and two electrons, X − ) charged excitons, and the decay dynamics of the other type of charged exciton is presumably estimated by the superposition principle of the biexciton Auger process. Herein, we demonstrate an opto-electrical method that enables us to precisely assess AR rates of X + and X − in core/shell heterostructured QDs. Specifically, we devise electron-only devices and hole-only devices to inject extra charge carriers into QDs without unwanted side reactions or degradation of QDs and probe AR characteristics of these charged QDs via timeresolved photoluminescence measurements. We find that AR rates of charged excitons, both X + and X − , gained from the present method agree well with those attained from conventional approaches and the superposition principle, corroborating the validity of the present approach. This present method permits us to comprehend multicarrier dynamics in QDs, prompting the use of QDs in light-emitting diodes and laser devices based on QDs.

The quantum dot light‐emitting diode (QLED) represents one of the strongest display technologies and has unique advantages like a shallow emission spectrum and superior performance based on the cumulative studies of state‐of‐the‐art quantum dot (QD) synthesis and interfacial engineering. However, research on managing the device's light extraction has been lacking compared to the conventional LED field. Moreover, relevant studies on top‐emitting QLEDs (TE‐QLEDs) have been severely lacking compared to bottom‐emitting QLEDs (BE‐QLEDs). This paper demonstrates a novel light extraction structure called the randomly disassembled nanostructure (RaDiNa). The RaDiNa is formed by detaching polydimethylsiloxane (PDMS) film from a ZnO nanorod (ZnO NR) layer and laying it on top of the TE‐QLED. The RaDiNa‐attached TE‐QLED shows significantly widened angular‐dependent electroluminescence (EL) intensities over the pristine TE‐QLED, confirming the effective light extraction capability of the RaDiNa layer. Consequently, the optimized RaDiNa‐attached TE‐QLED achieves enhanced external quantum efficiency (EQE) over the reference device by 60%. For systematic analyses, current–voltage–luminance (J–V–L) characteristics are investigated using scanning electron microscopy (SEM) and optical simulation based on COMSOL Multiphysics. It is believed that this study's results provide essential information for the commercialization of TE‐QLEDs.