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This study investigates the optical properties (light reflectance, absorptance, transmittance, and scattering) of black silicon (b‐Si) layers formed using reactive ion etching method. The corresponding spectra are determined across the visible, near‐infrared, and near‐ultraviolet wavelength ranges (250–1400 nm). It is demonstrated that b‐Si layers reduce the reflectance, and increase the absorptance and light scattering due to the disordered distribution of the nanoneedles. Increasing the etching duration strengthens this trend. It is shown that b‐Si layers etched for 10 min can be considered perfect light scatterers upon reflection at wavelengths less than 700 nm. Based on the obtained results, the possible profits of light scattering from the b‐Si interlayer for perovskite/Si tandem solar cells are analyzed. It is substantiated that the b‐Si interlayer can increase the useful absorptance not only within the bottom Si solar subcell but also in the top perovskite solar subcell. The prospects for future research directions and challenges are also provided. [ABSTRACT FROM AUTHOR]

Black silicon (BS) layers coated with passivation films are widely used as antireflective frontal surfaces for solar cells. The most common BS fabrication techniques are reactive ion etching (RIE), metal‐assisted chemical etching, and laser‐induced processing. Herein, the structural and optical properties, as well as the minority carrier lifetime, of BS are compared with and without atomic layer deposited HfO2 passivation films produced by the above formation methods. The antireflection behavior of the samples is discussed based on the light trapping effect and the change in the BS refractive index from air to the bulk of crystalline Si. Finally, test solar cells are manufactured, and their photovoltaic parameters are studied. The comparison results show that RIE is the most preferred in all technical respects. The features of using different BS fabrication techniques from the solar cell manufacturing point of view are analyzed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The photoelectric characteristics of a silicon structure with oppositely directed potential barriers are studied under longitudinal illumination. The choice of the impurity density in the n+–p–n+ regions ensure the joining of the depleted regions in the base. When a bias voltage is applied, the width of the regions varies at the expense of one another. During the temperature annealing (950 °C, for 20 min) of the guard band, the structure acquires short-wave (λ = 570 nm) and long-wave (λ = 850 nm) spectral photosensitivity, the numerical values of which turn out to be unusually high-up to 4 A/W and 1.2 A/W, respectively. The apparent internal amplification of the photocurrent is explained by the injection of the photogenerated carriers through the forward-biased potential barrier, which leads to a decrease in the height of both potential barriers. The internal amplification of the photocurrent up to four orders of magnitude is indicated by the ratio of the actual measured spectral photocurrent to the photocurrent calculated at the quantum yield equal to 1. The samples are characterized by low power levels equivalent to noise levels lower than 10–12 W Hz−1/2 cm2. [ABSTRACT FROM AUTHOR]

A study on the formation of black silicon (b-Si) antireflection layers on crystalline Si wafers using SF6/O2gas mixture in a reactive ion etching method is presented. The process is low-temperature, fast and does not depend on the crystallographic orientation of the Si wafer. The b-Si layers have demonstrated average reflectance values of 4% and 5% for monoand polycrystalline Si wafers respectively, feature that is suitable for the fabrication of high efficiency solar cells. Passivation of b-Si antireflection layers by suitable different thin films can significantly reduce needle-like surface recombination losses.