Dual‐ion batteries have been developed as a promising technology in recent years, but their high self‐discharge rate leading to low coulombic efficiency (CE) limits their practical applications. This work provides a deft strategy to circumvent this issue by using FeFe(CN)6 as the anode material for hosting Na+ cations, in combination with a graphite cathode for accommodating the bis(trifluoromethanesulfonyl)imide anions (TFSI−). The relatively high bonding force between FeFe(CN)6 and Na+ can hinder self‐extraction of ions from the electrodes, thereby decreasing the self‐discharge rate. The FeFe(CN)6 nanospheres, synthesized by a facile solution reaction method, are well crystallized and dispersed. Na+ insertion into the FeFe(CN)6 cube is determined by cyclic voltammetry (CV), galvanostatic charge–discharge, and X‐ray diffraction tests, suggesting a reversible process. Under a current of 0.05 mA cm−2 the batteries present an acceptable discharge plateau within 1.5–0.7 V and a well‐defined capacity of 75.0 mAh g−1, with a high CE above 98.5% (±0.1%); under 0.2 mA cm−2, cells display a high cyclability of 83.0% capacity retention for 100 cycles, with an excellent CE exceeding 99.6% (±0.1%). Moreover, the batteries exhibit a low self‐discharge rate with a resting capacity decay of 0.32% h−1, outperforming many of the reported dual‐ion cells.

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A 1280 × 1,024 In0.53Ga0.47As short wave infrared (SWIR) focal plane array (FPA) detector with a planar-type back-illuminated process has been fabricated. With indium bump flip-chip bonding techniques, the InGaAs photodiode arrays were hybrid-integrated to the CMOS readout integrated circuit (ROIC) with correlated double sampling (CDS). The response spectrum is 0.9–1.7 μm. The test results show that the dark current density is 2.25 nA/cm2 at 25 °C, the detectivity D* is up to 1.1 × 1013 cm · Hz1/2/W, the noise electron is as low as 48 e− under correlated double sampling mode, the quantum efficiency is 88% at 1550 nm, and the operability is more than 99.9%. Moreover, the dark current and noise electron have been studied theoretically in depth. The results indicate that the diffusion current is the main contribution of the dark current, and the readout integrated circuit noise electron is the main source of FPA noise.

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Gated InGaAs avalanche photodiodes are often used for synchronous single-photon detection in the near-infrared wavelengths of 1310 and 1550 nm for optical fiber communication. However, one of the main obstacles limiting their application is the difficulty in extracting a weak photon-induced avalanche pulse from background noise. Here, we describe a double-pulse superposition technique to detect the signal, which uses a synchronized pulse to raise the avalanche signal above the discriminating threshold so the avalanche signal can be easily detected. This technique provides a simple idea for a practical gated single-photon detector to sense avalanche signals since the parasitic capacitance signal from an applied external circuit is unavoidable and will always be coupled to the avalanche signal. Under the same measurement conditions, a comparison was made with the conventional capacitive balance technique, and the experimental results showed a high agreement between the effects of the two signal extraction techniques under several nanoseconds scale gating widths, and the doublepulse superposition technique is highly efficient and easy to implement even under complicated background noise.

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The relationship between the performance of avalanche photodiode (APD) and structural parameters of the absorption, grading, and multiplication layers has been thoroughly simulated and discussed using the equivalent materials approach and Crosslight software. Based on separate absorption, grading, charge, and multiplication (SAGCM) structure, the absorption layer of APD was replaced with InGaAs/GaAsSb superlattice compared to conventional InGaAs/InP SAGCM APD. The results indicated that the breakdown voltage increased with the doping concentration of the absorption layer. When the thickness of the multiplication layer increased from 0.1 μm to 0.6 μm, the linear range of punchthrough­­­ voltage increased from 16 V to 48 V, and the breakdown voltage decreased at first and then increased when the multiplication layer reached the critical thickness at 0.35 μm. The grading layer could not only slow down the hole carrier, but also adjust the electric field. The dark current was reduced to about 10 nA and the gain was over 100 when the APD was cooled to 240 K. The response wavelength APD could be extended to 2.8 μm by fine tuning the superlattice parameters. The simulation results indicated that the APD using superlattice materials has potential to achieve a long wavelength response, a high gain, and a low dark current.

The resolution of InGaAs FPA detectors is degraded by the electrical crosstalk, which is especially severe in high–density FPAs. We propose a guard-hole structure to suppress the electrical crosstalk in a planar-type 640 × 512 15 μm InGaAs short wavelength infrared FPA detector. For comparison, the frequently used guard ring is also prepared according to the same processing. The calculation results show that the electrical crosstalk with a guard hole is suppressed from 13.4% to 4.5%, reducing by 66%, while the electrical crosstalk with a guard ring is suppressed to 0.4%. Furthermore, we discuss the effects of the guard ring and the guard hole on the dark current, quantum efficiency, and detectivity. Experimental results show the detector with a guard-hole structure has higher performance compared with the detector with a guard-ring structure, the dark current density is reduced by 60%, the QE is increased by 64.5%, and the detectivity is increased by 1.36 times, respectively. The guard-hole structure provides a novel suppression method for the electrical crosstalk of high-density InGaAs detectors.