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Effective light scattering, transmission and absorption play a pivotal role in optical devices. Significant progress has been recorded in this area via the application of surface texturing techniques and photo-friendly thin film coatings. Combining two facile and environmentally safe synthesis processes, a textured silicon (Si)/amorphous carbon (a-C) nanocomposite coating was formed on single crystal silicon substrates. A high purity silicon coating with the average thickness of 17 μm was formed via in situ magnesiothermic reduction reaction (MRR) of diatomaceous earth (DE) and spherical nanosilica at 750 °C and followed by a facile phase separation between polyacrylonitrile (PAN)/tetraethyl orthosilicate (TEOS) to create a porous a-C film. The porous/continuous PAN thin films were subsequently carbonized at 850 °C resulting in a textured Si/a-C film nanocomposite. Unlike polished or textured silicon surfaces, the a-C coated textured silicon surface showed high broadband absorption in excess of 60% in the range 300–1700 nm that compares well with most textured surfaces reported recently in the literature, and benefits from a facile and eco-friendly fabrication approach.
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•Mg2Si formation is crucial for synthesizing textured silicon coatings.•High absorption of textured silicon coating is restricted to the visible spectral range.•Tunable porosity induces anti-reflective ability of carbon upper layer.•Broadband absorption achieved in nanostructured silicon coating with amorphous carbon upper layer.•Synergy between total internal reflection and refractive index promotes broadband absorption.