Aluminum Halide-Based Electron-Selective Passivating Contacts for Crystalline Silicon Solar Cells.

Extensive research has focused on developing wide-bandgap metal compound-based passivating contacts as alternatives to conventional doped-silicon-layer-based passivating contacts to mitigate parasitic absorption losses in crystalline silicon (c-Si) solar cells. Herein, thermally-evaporated aluminum halides (AlX)-based electron-selective passivating contacts for c-Si solar cells are investigated. A low contact resistivity of 60.5 and 38.4 mΩ cm2 is obtained on the AlClx/n-type c-Si (n-Si) and AlFx/n-Si heterocontacts, respectively, thanks to the low work function of AlX. Power conversion efficiencies (PCEs) of 19.1% and 19.6% are achieved on proof-of-concept n-Si solar cells featuring a full-area AlClx/Al and AlFx/Al passivating contact, respectively. By further implementing an ultrathin SiO2 passivation interlayer and a pre-annealing treatment, the electron selectivity (especially the surface passivation) of AlX is significantly enhanced. Accordingly, a remarkable PCE of 21% is achieved on n-Si solar cells featuring a full-area SiO2/AlFx/Al rear contact. AlFx-based electron-selective passivating contacts exhibit good thermal stability up to ≈400 °C and better long-term environmental stability. This work demonstrates the potential of AlFx-based electron-selective passivating contact for solar cells.

Design of a Micro-Electro Mechanical System Quad Mass Gyroscope with Compliant Mechanical Amplification.

In this work, a novel mechanical amplification structure for a MEMS vibratory gyroscope is proposed with the aim of improving their sensitivity. The scheme is implemented using a system of micromachined V-shaped springs as a deflection amplifying mechanism. The effectiveness of the mechanism is first demonstrated for a capacitive fully decoupled quad mass gyroscope. A proof of concept vertical-axis mechanically amplified gyroscope with an amplification factor of 365% has been designed, simulated and fabricated, and results from its evaluation are presented in this paper. Experimental results show that the natural frequency of the gyroscope is 11.67 KHz, and the full scale measurement range is up to ±400°/s with a maximum nonlinearity of 54.69 ppm. The bias stability is 44.53°/h. The experiment results show that this quad mass gyroscope's performance is a very potential new way of reaching the navigation grade in the future.

Design and Implementation of an Event-Driven Smart Sensor Node for Wireless Monitoring Systems.

In this paper, an event-driven wireless sensor node is proposed and demonstrated. The primary design objective is to devise a wireless sensor node with miniaturization, integration, and high-accuracy recognition ability. The proposed wireless sensor node integrates two vibration-threshold-triggered energy harvesters that sense and power a threshold voltage control circuit for power management, a microcontroller unit (MCU) for system control, a one-dimensional convolutional neural network (1D-CNN) environment data analysis and vibration events distribution, and a radio frequency (RF) digital baseband transmitter with IEEE 802.15.4-/.6 protocols. The dimensions of the wireless sensor node are 4 × 2 × 1 cm3. Finally, the proposed wireless sensor node was fabricated and tested. The alarming time for detecting the vibration event is less than 6 s. The measured recognition accuracy of three events (knock, shake, and heat) is over 97.5%. The experimental results showed that the proposed integrated wireless sensor node is very suitable for wireless environmental monitoring systems.