One-dimensional semiconductor nanostructures as absorber layers in solar cells

The one-dimensional (1-D) nanostructures of cadmium chalcogenides (II-VI: CdSe, CdTe), InP and GaAs (III-V), and the ternary chalcopyrites CulnS ₂, CulnSe ₂, and CulnTe ₂ (I-III-VI ₂) are the candidate semiconductors of interest as absorber layers in solar cells. In the confinement regime (∼1-10 nm) of these 1-D nanostructures, the electronic energy levels are quantized so that the oscillator strength and the resultant absorption of solar energy are enhanced. Moreover, the discrete energy levels effectively separate the electrons and holes at the two electrodes or at the interfaces with a polymer in a hybrid structure, so that an oriented and 1-D nanostructured absorber layer is expected to improve the conversion efficiency of solar cells. The intrinsic anisotropy of II-VI and I-III-VI ₂ crystal lattices and the progress in various growth processes are assessed to derive suitable morphological features of these 1-D semiconductor nanostructures. The present status of research in nanorod-based solar cells is reviewed and possible routes are identified to improve the performance of nanorod-based solar cells. Finally, the characteristics of nanorod-based solar cells are compared with the dye-sensitized and organic solar cells.