Density Functional Theory Studies on Dimension-Controlled Self-Assemblies from Cadmium Telluride Nanoclusters: Implications for Solar Cell Applications

We report a first-principles theory-based study of the stability, electronic structure, and optical properties of cluster-assembled materials in various one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) nanostructures using a cagelike Cd9Te9 cluster as the superatom. The bulk 3D self-assemblies form in 2D stacked structures for different cubic lattices. The face-centered stacking is the most stable compared to the simple cubic, body-centered, and zinc blende-type stackings. The 2D stacks are formed as cluster-assembled monolayers, and the monolayer derived from the face-centered structure is the most stable. Further, the cluster chains (or wires) with more number of intercluster bonds are also seen to be dynamically stable. Due to quantum confinement, the energy gap of CdTe self-assemblies increases from the 3D to 2D to 1D nanostructures. The electronic structure, band gap, dielectric constant, and absorption spectra along with the phonon dispersions are discussed for these self-assembled nanostructures. The dielectric properties of these self-assembled nanostructures point to their potential applications in fabricating solar cells.