Broadband Visible‐Light Absorber With Exceptional Optical Efficiency for Semiconductor Optoelectronic Devices

Parasitic optical reflection critically limits the performance of semiconductor optoelectronic devices. While ultra‐black materials offer a solution, the relationship between anti‐reflection properties and device integration performance has rarely been studied. This work develops a series of robust, graded‐refractive index ultra‐black coatings compatible with semiconductor processing. A conventional carbon black (CB)/polydimethylsilane (PDMS) film is enhanced with three distinct anti‐reflective designs: single‐layer (SL), bilayer (BL), and a trilayer (TL, Al 2 O 3 /TiO 2 /SiO 2 ) structure. The TL coating achieves an ultra‐low reflectivity of 0.16% at 536 nm. The impact of these coatings is systematically investigated by integrating them into two disparately representative devices: reducing carriers in thin‐film transistors (TFTs) and thermoelectric generators. Results demonstrate that the ultra‐black films effectively suppress photogenerated leakage current in TFTs caused by parasitic optical reflection while simultaneously enhancing the photothermal conversion efficiency in thermoelectric devices. This study provides a versatile strategy for developing high‐performance anti‐reflective coatings and contributing theoretical insights for their application in next‐generation optoelectronic and energy‐harvesting systems.