The group created a densely packed, side-by-side array of miniature electrodes on top of transparent glass that separates the light-harvesting and charge-conducting functions. With a fill factor of 60%, the cells acheive a conversion efficiency of 5.2%, compared to 1.8% for other lateral cell designs.
"From a fabrication point of view, it is always going to be easier to make side-by-side structures," says Hongrui Jiang, a UW-Madison professor of electrical and computer engineering and an author on the paper. "Top-down structures need to be made in multiple steps and then aligned, which is very challenging at small scales. We easily beat all of the other lateral structures.
"In other structures, a lot of volume goes wasted because there are no electrodes or the electrodes are mismatched. The technology we developed allows us to make very compact lateral structures that take advantage of the full volume."
Jiang and colleagues are working to make their solar cells even smaller and more efficient by exploring materials that further optimize transparency and conductivity. Ultimately they plan to develop a small-scale, flexible solar cell that could provide power to an electrically tunable contact lens.