Effect of Fe doping on the crystallinity of CuO nanotubes and the efficiency of the hybrid solar cells

We have synthesized CuO nanotubes (NTs) by wet chemical method and studied the effect of Fe-doping on the electro-optical properties. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements suggest a diameter of ∼40–50 nm for the as synthesized un-doped NTs; however Fe doping increases the diameters to ∼60–70 nm. Energy dispersive X-ray (EDX) analysis confirmed that CuO and Fe-doped CuO NTs have been successfully synthesized by wet-chemical route. X-rays diffraction (XRD) patterns also suggest that by increasing the Fe content the size of the NTs increases thereby improving the crystallinity. These observations are consistent with the steady-state photoluminescence measurements where a decrease in the emission intensity from deep defect states has been observed for Fe-doped CuO NTs. UV–vis absorption studies suggest a band gap of ∼2.6 eV for CuO NTs. Moreover, by increasing the Fe dopant content a blue shift of 300 meV has been observed due to the Burstein-Moss effect. The hybrid solar cells containing CuO and Fe-doped CuO NTs and poly-3-hexyl thiophene (P3HT) are prepared and their efficiency has been evaluated.