Structural, Electronic Structure, and Photovoltaic Studies of MgO/TiO2/ITO Heterostructures

This study describes the mechanism of interfacial interaction of the MgO layer with TiO2 films and demonstrates the modification in optical and photovoltaic properties of MgO/TiO2/ITO heterostructures. X-ray diffraction, field emission scanning electron microscopy (FESEM), UV-visible spectroscopy, and x-ray absorption near-edge structure (XANES) at O K-edge, Mg K-edge, and Ti K-edge have been employed to characterize the MgO/TiO2/ITO heterostructures. The photovoltaic properties of heterostructures are studied using a solar simulator. FESEM results confirmed the spherical shape of MgO and TiO2 nanoparticles. Hybridization among the frontier orbitals of O, Mg, and Ti and the presence of Mg2+ and Ti4+ ions are confirmed by XANES studies. Assimilation of the MgO layer on TiO2 film resulted in a significant enhancement in the absorbance characteristics. The MgO film, deposited with maximum spin-coating speed 5000 rpm, exhibited the highest fill factor (FF=0.78), high short-circuit current (I-sc = 12.20 mA/cm(2)), and open-circuit voltage (V-oc = 0.93 V). The mechanism of high FF in MgO/TiO2/ITO structures has been discussed by considering the transparency and electron scavenging from the heterostructures.