Black silicon (b‐Si) has many attractive properties and is currently being adopted in various fields of semiconductor technology. It is shown here that b‐Si during thermal activation may serve as an external gettering layer to remove metallic impurities and associated defects from bulk Si. The gettering efficiency by b‐Si is estimated according to the results of studying the resistivity, defect density, interstitial iron concentration, and effective minority carrier lifetime on gettered test and ungettered reference Si samples. It is shown that in the thermal oxidation process, the b‐Si layer serves as an effective drain for excess iron atoms and other fast‐diffusing impurities, thereby significantly reducing the density of oxidation‐induced stacking faults in Si. In addition, the resistivity of the substrates decreases, and the bulk carrier lifetime increases significantly. Finally, gettering by b‐Si is introduced into the solar cells fabrication process and its effect on solar cell current–voltage characteristics is investigated. It has been shown that all electronic parameters of the solar cells are improved. The conversion efficiency of ungettered solar cells is 16.8%, and for gettered solar cells, depending on the oxidation temperature, it increases by 1.36–1.96%.
Nitrogen dioxide (NO2) is a serious environmental pollutant and can cause negative consequences on both human health and vegetation growth. Herein, the possibility and promise of using a resistive sensor based on pristine black silicon (BSi) to detect NO2 at room temperature are investigated. BSi is prepared using plasma‐based reactive ion etching. Scanning electron microscope (SEM) studies show that BSi consists of vertically standing nanoneedles and has a large surface area, which facilitates gas adsorption. The gas‐sensing properties of the BSi‐based sensor are tested for low NO2 concentrations (1–5 ppm). It is found that the prepared sensor samples without posttreatments of BSi exhibit high sensitivity, fast transient response, and good repeatability. In particular, the response and recovery time of the sensor are ≈35 and ≈25 s for 4 ppm NO2 gas exposure, respectively. Besides, the results indicate that the BSi‐based sensor has excellent selectivity. Finally, the sensing mechanism is discussed, the dominating factors of which are the large active sensing area and the vertical arrangement of the BSi nanoneedles. It is believed that with further optimization, BSi has good potential as a functional material for gas sensors.
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