Achieving near-perfect light absorption in atomically thin transition metal dichalcogenides through band nesting

Molybdenum disulfide (MoS₂) is a promising material for atomically thin perfect absorbers due to the high oscillator strength of its excitonic transitions and excellent band nesting. MoS2 is a strong absorber of light in the violet spectral range due to band nesting, but this absorption is not sufficient to create a near-perfect light absorber, since natural bi-layers disrupt the band nest effect due to interlayer interactions. Most approaches to improving the light-matter interaction of MoS₂ have been devoted to plasmonic structures or patterned meta-surfaces, which require complex nanolithography, limiting their practical application.



Here, we describe an approach where band nesting is used to realize near-perfect light absorbers (NPLAs) with only two or three layers without any complex nanostructures. The primary innovation in our design is to stack two layers of MoS₂ to minimize interlayer coupling and preserve their individual band nesting characteristics. Two structures are evaluated: (1) twisted bi-layer MoS₂ and (2) two MoS₂ layers with a buffer layer in between. Combining these structures with a Salisbury screen geometry, we demonstrate NPLAs with absorption of up to 95% at a photon energy of 2.8 eV. Moreover, theoretical studies suggest that absorption can be as high as 99% and that NPLAs can be realized at various wavelengths using different combinations of 2D materials.