Effect of temperature in the sol–gel method on the morphology of the ZnO layer used as a window layer in the PbS quantum dot solar cells

In this study, we investigated the effect of temperature in the production stage of zinc oxide (ZnO) sol on the morphology of the ZnO layer prepared by the sol-gel spin coating process. Zinc acetate dihydrate was used as the precursor material. 2-Methoxyethanol and monoethanolamine (MEA) were used as a solvent and stabilizer, respectively. Sol was prepared by stirring the solution for 2 h at different temperatures, from room temperature to 60°C. Energy dispersive spectroscopy, surface morphology and cross-sectional microstructure were studied by scanning electron microscopy. Evidence showed that reducing the stirring temperature to a specific temperature improves the morphology of the ZnO coating layer. Scanning electron microscope images of the cross-section showed that the thickness of the coating layer did not depend on the sol preparation temperature. The results of particle size analysis showed that with decreasing temperature from 60 to 50°C, the particle size of the sol becomes smaller, and the sol becomes more homogeneous. Current-voltage diagrams show that improving the morphology of the ZnO window layer improves the performance of PbS quantum dot solar cells. (author)