RESUMEN
An automotive 2.1 µm CMOS image sensor has been developed with a full-depth deep trench isolation and an advanced readout circuit technology. To achieve a high dynamic range, we employ a sub-pixel structure featuring a high conversion gain of a large photodiode and a lateral overflow of a small photodiode connected to an in-pixel storage capacitor. With the sensitivity ratio of 10, the expanded dynamic range could reach 120 dB at 85 °C by realizing a low random noise of 0.83 e- and a high overflow capacity of 210 ke-. An over 25 dB signal-to-noise ratio is achieved during HDR image synthesis by increasing the full-well capacity of the small photodiode up to 10,000 e- and suppressing the floating diffusion leakage current at 105 °C.
RESUMEN
Organic-inorganic hybrid perovskite nanoparticles (NPs) are a very strong candidate emitter that can meet the high luminescence efficiency and high color standard of Rec.2020. However, the instability of perovskite NPs is the most critical unsolved problem that limits their practical application. Here, an extremely stable crosslinked perovskite NP (CPN) is reported that maintains high photoluminescence quantum yield for 1.5 years (>600 d) in air and in harsher liquid environments (e.g., in water, acid, or base solutions, and in various polar solvents), and for more than 100 d under 85 °C and 85% relative humidity without additional encapsulation. Unsaturated hydrocarbons in both the acid and base ligands of NPs are chemically crosslinked with a methacrylate-functionalized matrix, which prevents decomposition of the perovskite crystals. Counterintuitively, water vapor permeating through the crosslinked matrix chemically passivates surface defects in the NPs and reduces nonradiative recombination. Green-emitting and white-emitting flexible large-area displays are demonstrated, which are stable for >400 d in air and in water. The high stability of the CPN in water enables biocompatible cell proliferation which is usually impossible when toxic Pb elements are present. The stable materials design strategies provide a breakthrough toward commercialization of perovskite NPs in displays and bio-related applications.
RESUMEN
Recently, the structural stability of all-inorganic halide perovskite nanocrystals has been significantly enhanced. To understand the enhancement, we developed surface-passivation models for cubic CsPbBr3 nanocrystals with anionic (oleate) and cationic (oleylammonium) organic ligands based on first-principles calculations and nuclear magnetic resonance investigations. We propose that the (100) surface is initially terminated with oleate ligand complexes on PbBr2(100) surfaces. Also, the ligand transition to oleylammonium on the Pb-rich surfaces is expected due to the addition of metal halides (ZnBr2) during colloidal synthesis. The significant improvement in the structural stability of the cationic ligand-passivated CsPbBr3 nanocrystals was attributed to the suppressed exposure of the merging-vulnerable (110) surface, caused by the large difference in formation energy between the ligand-passivated (100) and Br-passivated (110) surfaces.
RESUMEN
We formulated atomic models of cation-rich surfaces passivated with anionic ligands for IV-VI, II-VI, and III-V colloidal quantum dots, employing electron counting models and quantum mechanical calculations. We found that the fractional dangling bonds of cation-rich (100) and (111) surfaces could be greatly stabilized by dimerization-anion passivation and amine-anion co-passivation.
RESUMEN
Wet chemical synthesis of covalent III-V colloidal quantum dots (CQDs) has been challenging because of uncontrolled surfaces and a poor understanding of surface-ligand interactions. We report a simple acid-free approach to synthesize highly crystalline indium phosphide CQDs in the unique tetrahedral shape by using tris(dimethylamino) phosphine and indium trichloride as the phosphorus and indium precursors, dissolved in oleylamine. Our chemical analyses indicate that both the oleylamine and chloride ligands participate in the stabilization of tetrahedral-shaped InP CQDs covered with cation-rich (111) facets. Based on density functional theory calculations, we propose that fractional dangling electrons of the In-rich (111) surface could be completely passivated by three halide and one primary amine ligands per the (2×2) surface unit, satisfying the 8-electron rule. This halide-amine co-passivation strategy will benefit the synthesis of stable III-V CQDs with controlled surfaces.
