Precise microscale patterning is a prerequisite to incorporate the emerging colloidal metal halide perovskite nanocrystals into advanced, integrated optoelectronic platforms for widespread technological applications. Current patterning methods suffer from some combination of limitations in patterning quality, versatility, and compatibility with the workflows of device fabrication. This work introduces the direct optical patterning of perovskite nanocrystals with ligand cross-linkers or DOPPLCER. The underlying, nonspecific cross-linking chemistry involved in DOPPLCER supports high-resolution, multicolored patterning of a broad scope of perovskite nanocrystals with their native ligands. Patterned nanocrystal films show photoluminescence (after postpatterning surface treatment), electroluminescence, and photoconductivity on par with those of conventional nonpatterned films. Prototype, pixelated light-emitting diodes show peak external quantum efficiency of 6.8% and luminance over 20,000 cd m −2 . Both are among the highest for patterned perovskite nanocrystal devices. These results create new possibilities in the system-level integration of perovskite nanomaterials and advance their applications in various optoelectronic and photonic platforms.
The challenge of controllable chemical synthesis of aluminum nanocrystals (Al NCs) has been met with only limited success. A major barrier is the absence of effective ligands to control the nucleation and growth of Al NCs.Here we demonstrate the size-and shape-controlled synthesis of monodisperse Al NCs using a polymer ligand, cumyl dithiobenzoate-terminated polystyrene (CDTB-PS). Density functional theory (DFT) calculations indicate that CDTB-PS shows selective absorption on Al{100} facets, inducing the formation of nanocubes and trigonal bipyramids. An excess of CDTB-PS, however, decreases the supersaturation of Al atoms, leading to the formation of {111} facetterminated octahedral and triangular plates. The concentration of the catalyst, titanium (IV) isopropoxide, determines the size of Al NCs by controlling the number of seeds. Depending on nanoparticle size, the solutions of Al NCs possess distinct colors, a characteristic feature of plasmonic nanomaterials. This robust and controlled chemical synthesis of Al NCs lays a foundation for Al as a sustainable plasmonic material for current and future applications.
Surface chemistry mediated direct optical patterning represents an emerging strategy for incorporating colloidal nanocrystals (NCs) in integrated optoelectronic platforms including displays and image sensors. However, the role of photochemistry of crosslinkers and other photoactive species in patterning remains elusive. Here we show the design of nitrene‐ and carbene‐based photocrosslinkers can strongly affect the patterning capabilities and photophysical properties of NCs, especially quantum dots (QDs). Their role beyond physical linkers stems from structure‐dictated electronic configuration, energy alignment and associated reaction kinetics and thermodynamics. Patterned QD layers with designed carbene‐based crosslinkers fully preserve their photoluminescent and electroluminescent properties. Patterned light emitting diodes (QLEDs) show a maximum external quantum efficiency of ≈12 % and lifetime over 4800 h, among the highest for reported patterned QLEDs. These results would guide the rational design of photoactive species in NC patterning and create new possibilities in the monolithic integration of NCs in high‐performance device platforms.
Precise patterning with microscale lateral resolution and widely tunable heights is critical for integrating colloidal nanocrystals into advanced optoelectronic and photonic platforms. However, patterning nanocrystal layers with thickness above 100 nm remains challenging for both conventional and emerging direct photopatterning methods, due to limited light penetration depths, complex mechanical and chemical incompatibilities, and others. Here, we introduce a direct patterning method based on a thermal mechanism, namely, the thermally activated ligand chemistry (or TALC) of nanocrystals. The ligand cross-linking or decomposition reactions readily occur under local thermal stimuli triggered by near-infrared lasers, affording high-resolution and nondestructive patterning of various nanocrystals under mild conditions. Patterned quantum dots fully preserve their structural and photoluminescent quantum yields. The thermal nature allows for TALC to pattern over 10 μm thick nanocrystal layers in a single step, far beyond those achievable in other direct patterning techniques, and also supports the concept of 2.5D patterning. The thermal chemistry-mediated TALC creates more possibilities in integrating nanocrystal layers in uniform arrays or complex hierarchical formats for advanced capabilities in light emission, conversion, and modulation.
Aluminum nanocrystals (Al NCs) are sustainable plasmonic nanomaterials with unique localized surface plasmonic resonance (LSPR) in the ultraviolet (UV) region. Chemical synthesis of sub-100-nm Al NCs remains a considerable challenge due to the lack of effective ligands to control their growth. Here, we describe a precise size-controlled synthesis of small colloidal Al NCs (25-100 nm) with strong and tunable LSPR peak from 250 to 372 nm in the UV spectral region by the use of poly(ethylene oxide) (PEO) as a polydentate surface ligand. The LSPR band matched well with the numerical simulation results. Additionally, the molecular weight of the PEO played an essential role in tuning the size of Al NCs. The PEO showed a strong affinity with Al {111} crystal facets, resulting in octahedral-and prism-shaped Al NCs. Owing to the passive oxide layer generated on the surface of Al NCs, their LSPR peak positions showed negligible changes after storage in tetrahydrofuran for 4 months. The passivation layer also impeded the metal Al core to react with deionized water. Further, the use of biocompatible PEO ligand and the subsequent generation of the sub-100-nm size of the Al NCs pave a path for bioapplications of such NCs.
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