The poly-Si carrier-selective passivating contacts (CSPCs) parasitically absorb a substantial amount of light, especially in the form of free carrier absorption. To minimize these losses, we developed CSPCs based on oxygen-alloyed poly-Si (poly-SiOx) and deployed them in c-Si solar cells. Transmission electron microscopy analysis indicates the presence of nanometer-scale silicon crystals within such poly-SiOx layers. By varying the O content during material deposition, we can manipulate the crystallinity of the poly-SiOx material and its absorption coefficient. Also, depending on the O content, the bandgap of the poly-SiOx material can be widened, making it transparent for longer wavelength light. Thus, we optimized the O alloying, doping, annealing, and hydrogenation conditions. As a result, an extremely high passivation quality for both n-type poly-SiOx (J0 = 3.0 fA/cm2 and iVoc = 740 mV) and p-type poly-SiOx (J0 = 17.0 fA/cm2 and iVoc = 700 mV) is obtained. A fill factor of 83.5% is measured in front/back-contacted solar cells with both polarities made up of poly-SiOx. This indicates that the carrier transport through the junction between poly-SiOx and c-Si is sufficiently efficient. To demonstrate the merit of poly-SiOx layers' high transparency at long wavelengths, they are deployed at the back side of interdigitated back-contacted (IBC) solar cells. A preliminary cell efficiency of 19.7% is obtained with much room for further improvement. Compared to an IBC solar cell with poly-Si CSPCs, a higher internal quantum efficiency at long wavelengths is observed for the IBC solar cell with poly-SiOx CSPCs, thus demonstrating the potential of poly-SiOx in enabling higher JSC.
This paper presents a pitch-matched transceiver ASIC integrated with a 2-D transducer array for a wearable ultrasound device for transfontanelle ultrasonography. The ASIC combines 8-fold multiplexing, 4-channel microbeamforming (μBF) and sub-array-level digitization to achieve a 128-fold channel-count reduction. The μBF is based on passive boxcar integration and interfaces with a 10-bit 40 MS/s SAR ADC in the charge domain, thus obviating the need for explicit anti-alias filtering and power-hungry ADC drivers. A compact and low-power reference generator employs an areaefficient MOS capacitor as a reservoir to quickly set a reference for the ADC in the charge domain. A low-power multi-level data link concatenates outputs of four ADCs, leading to an aggregate 3.84 Gb/s data rate. Per channel, the RX circuit consumes 2.06 mW and occupies 0.05 mm 2 .
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