Simulation Study on the Effect of Doping Concentrations on the Photodetection Properties of Mg2Si/Si Heterojunction Photodetector

To develop and design an environmentally friendly, low-cost shortwave infrared (SWIR) photodetector (PD) material and extend the optical response cutoff wavelengths of existing silicon photodetectors beyond 1100 nm, high-performance silicon-compatible Mg2Si/Si PDs are required. First, the structural model of the Mg2Si/Si heterojunction was established using the Silvaco Atlas module. Second, the effects of the doping concentrations of Mg2Si and Si on the photoelectric properties of the Mg2Si/Si heterojunction PD, including the energy band, breakdown voltage, dark current, forward conduction voltage, external quantum efficiency (EQE), responsivity, noise equivalent power (NEP), detectivity, on/off ratio, response time, and recovery time, were simulated. At different doping concentrations, the heterojunction energy band shifted, and a peak barrier appeared at the conduction band of the Mg2Si/Si heterojunction interface. When the doping concentrations of Si and Mg2Si layer were 1017, and 1016 cm−3, respectively, the Mg2Si/Si heterojunction PD could obtain optimal photoelectric properties. Under these conditions, the maximum EQE was 70.68% at 800 nm, the maximum responsivity was 0.51 A/W at 1000 nm, the minimum NEP was 7.07 × 10−11 WHz–1/2 at 1000 nm, the maximum detectivity was 1.4 × 1010 Jones at 1000 nm, and the maximum on/off ratio was 141.45 at 1000 nm. The simulation and optimization result also showed that the Mg2Si/Si heterojunction PD could be used for visible and SWIR photodetection in the wavelength range from 400 to 1500 nm. The results also provide technical support for the future preparation of eco-friendly heterojunction photodetectors.

Parametric modal analysis of an induced-strain actuated wing-like plate for pitch and heave coupling response

This article investigates the feasibility of a plate-like flapping wing with varying geometric and boundary conditions actuated by surface-bonded piezoelectric material devices. The most influential structural parameters that vary dynamic response and heave–pitch mode coupling are investigated. An analytically and experimentally validated dynamic finite element model is developed to analyze the structure. A parametric analysis is conducted by varying critical geometric parameters and boundary conditions, such as aspect ratio, actuator position, actuator angle, clamp size, and position; substrate thickness variation; and substrate-to-actuator-thickness ratio. Response metrics representing heave and pitch motions are taken as longitudinal curvature and lateral slope, respectively—the surface regression analysis and results leading to these choices are presented. Maximum longitudinal curvature and lateral slope amplitudes and phase shifts are reported for key parameter choices. Longitudinal curvature to lateral slope coupling is achieved with the introduction of a leading edge stiffener to the otherwise uniform thickness plate. Conditions and parameters that lead to and influence heave–pitch coupling are presented and discussed in detail. This article presents a unique approach to flapping mode of flight compared to the literature. The article proposes a purely induced-strain actuation approach rather than the typical “mechanisms” based approach.

Electrochromism in Electropolymerized Films of Pyrene-Triphenylamine Derivatives

Two star-shaped multi-triphenylamine derivatives 1 and 2 were prepared, where 2 has an additional phenyl unit between a pyrene core and surrounding triphenylamine units. The oxidative electropolymerization of 1 and 2 occurred smoothly to give thin films of polymers P1 and P2. The electrochemistry and spectroelectrochemistry of P1 and P2 were examined, showing two-step absorption spectral changes in the near-infrared region. The electrochromic properties, including contrast ratio, response time, and cyclic stability of P1 and P2 were investigated and compared. Thin film of P2 displays slightly better electrochromic performance than P1, with a contrast ratio of 45% at 1475 nm being achieved.

A high-sensitivity fluorescent probe with a self-immolative spacer for real-time ratiometric detection and imaging of alkaline phosphatase activity

The probe APW uses a self-immolative mechanism to achieve a ratio response to ALP, which has the following advantages: fast response (in less than 15 min), high quantum yield (Φ = 0.6), low detection limit (0.46 U L−1) and excellent selectivity.