Nanocomposite films for 13.57%-efficient organic solar cell

A Malaysian research group has fabricated an organic solar cell by using the solution-casting method, with varying concentrations of zinc oxide (ZnO) nanoparticles in a matrix of polyvinyl alcohol (PVA). The solution casting method is commonly used for casting nanocomposite polymer films and consists of merging, equally, a polymer and a prepolymer and making them soluble in a suitable solution.

In the development of their cell, the Malaysian scientists used ZnO as a prepolymer to improve the mechanical, electrical, and optical characteristics of the PVA polymer, which was prepared by adding deionized water. They claim this is the first time that ZnO/PVA nanocomposite films, which are well known for their good optoelectronic properties, are used in organic PV cells.

Different samples of the solution were kept in an oven at 40 degrees Celsius and 60  degrees Celsius, for one and two days, respectively. The selected samples had a size of 130×60mm and a thickness varying from 0.025mm to 0.1mm. These were applied to a basic organic cell based on a Copper(II) oxide (CuO) layer and a carbon-doped zinc oxide (C-ZnO) layer.

The cell was tested outdoors under the direct solar heat of 32 degrees Celsius at noontime at a Malaysian location. These measurements showed that the optical direct bandgap of the cell decreased with the increase in ZnO concentration in the polymer matrix, which also meant a loss in efficiency for the whole PV device. “The thickness of the ZnO/PVA nanocomposite film also affects the efficiency of organic solar cells and the efficiency decreases with the increase in thickness of ZnO/PVA nanocomposite film,” the academics further explained.

The highest efficiency, of 13.57%, was found in the cell with the lowest concentration of ZnO, which was 14.25%, while the lowest efficiencies were reported for the cell with the highest concentration of ZnO. Before applying the film, the efficiency of the best-performant cell was 10.07%.

“The optimum drying time needs to be determined in order to obtain nanocomposite thin film with better physical and chemical characteristics,” the researchers affirmed, noting that future work should be aimed at improving the quality of deposition of ZnO/PVA nanocomposite film. “The applications for this cell are not defined yet. However, due to its strength, it can be used in automotive roof applications,” research co-author, Shaheer Ahmed Khan, told pv magazine.

The cell is described in the paper Performance investigation of ZnO/PVA nanocomposite film for organic solar cell, published in materialstoday: Proceedings. The research group includes scientists from the International Islamic University Malaysia.