The conductive cover on a solar panel or touch screen display has to be clear. Thin, transparent films made of indium tin oxide (ITO) are suitable as conductive overlays.
A study carried out by researchers from Brown University and ATMI has yielded an economical and easy method to develop an ITO film that scores high on conductivity and transparency. This method is already at the performance stage for use in resistive touch screens.
The team of researchers made ITO films with thickness measuring 146 billionths of a meter which were deposited on glass plates. The film was found to allow 93% of the light to propagate through it. The films were made by synthesizing ITO nanocrystals in a solution and depositing the solution on to the glass plate by dripping followed by rapid spinning using a process called spin casting. The coated plates were annealed for few hours. The team found that annealing for a period of 6 h yields optimum results. The challenge in producing high performance films is in identifying the right chemical combination. The team found that indium acetylacetonate and tin bis (acetylacetonate) dichloride provided the best result as their consistency ensured that they form evenly distributed films to enhance conductivity rather than clumping together or spreading too far apart. The team demonstrated that transparency and resistance can be varied by controlling the film thickness and tin content. The thickness of the film was controlled by varying the concentration of the nanocrystal solution. The team is now working to improve conductivity performance to be on par with films produced by sputtering.