Highly enhanced solar conversion efficiency of novel layer-by-layer PbS:Hg and CdS quantum dots-sensitized ZnO thin films prepared by sol–gel spin coating

Abstract

Owing to superior optical properties, ZnO thin films have immense potential in solar cell preparation. ZnO thin films were prepared by sol-gel technology. However, this is prolonged technique and it necessitates a complex precursor solution. In the present work, ZnO thin films are prepared by sol-gel spin coating with simple precursor, zinc acetate. A very remarkable feature of the method is that polycrystalline, non-abrasive and translucent films were obtained. Additionally, novel PbS:Hg quantum dots (QDs) and CdS QDs are successfully synthesized. Moreover, both types of QDs are deposited layer-by-layer over pure ZnO and Ag:ZnO thin films. The films are characterized by X-ray diffraction, and crystallinity continuation is observed even after the addition of QDs layer. Presence of synthesized QDs over thin films is also confirmed. The films were also characterized by scanning electron microscopy (SEM) and UV-Vis spectroscopy. Uniform, dense and porous surface morphology is clearly revealed. Sensitized thin films show a huge decline in band gap and large enhancement in efficiency. Superior current density (10.87 mA cm −2) is achieved with PbS:Hg/CdS/Ag:ZnO, which leads to enhancement in overall solar conversion efficiency by 6.34 times.