Significant enhancement of optical absorption through nano-structuring of copper based oxide semiconductors: possible future materials for solar energy applications

Abstract

The optical absorption coefficient is a crucial parameter in determining solar cell efficiency under operational conditions. It is well known that inorganic nanocrystals are a benchmark model for solar cell nanotechnology, given that the tunability of optical properties and stabilization of specific phases are uniquely possible at the nanoscale. A hydrothermal method was employed to fabricate nanostructured copper oxides where the shape, size and phase were tailored by altering the growth parameters, namely the base media used, the reaction temperature, and the reaction time. The nano crystalline structures, phases, morphology, molecular vibrational modes, and optical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL), and UV-vis spectroscopy. A significantly large optical absorption coefficient, of the order of twice that of Si in the visible range, was observed in a particular phase mixture of nanostructured copper oxides. An optical absorption coefficient of 7.05 10⁺⁵ cm⁻¹ at 525 nm was observed in a particular nanostructured phase mixture of copper oxides which is appreciably larger than commercially pure CuO (1.19 10⁺⁵ cm⁻¹) and Si (1.72 10⁺⁵ cm⁻¹). A possible mechanism of formation of phase mixtures and morphology of copper oxides has also been discussed, which opens up a roadmap in synthesis of similar morphology nanostructures for efficient solar cells.