A new paper from the inventor of the dye sensitized solar cell suggests that inkjet printing may be the key to improving their performance.

Back in the late 1980’s, two Berkeley scientists invented the dye sensitized solar cell (DSSC). Formed by a thin layer of low-cost, dye-coated particles, sandwiched between two electrodes in an electrolyte, these cells can absorb a wide range of wavelengths. Now, one of those scientists has developed a new fabrication method that makes DSSCs even cheaper to produce, while retaining their performance.

Silicon-based solar cells are a rapidly-growing technology, with improving efficiencies both at lab-scale and for commercial devices. For now, cost remains at a premium, but alternatives (such as thin film photovoltaics) are going some way towards changing that. But a paper in this month’s issue of Nano Energy [DOI: 10.1016/j.nanoen.2015.08.019] goes further. Led by Michael Grätzel, a team of Swiss and Finnish researchers have developed a low-cost, inkjet-printed dye sensitized solar cell that outperforms those already available.

So how does it work? DSSCs are typically fabricated using standard thin film processes – first a layer of dye sensitized titanium dioxide is applied to a substrate and then topped with another electrode. Next, two holes are drilled in the top electrode and the liquid electrolyte inserted by suction. The holes are then sealed by topping the device with a foil and a glass cover. Grätzel’s new approach is different – instead of being injected, the electrolyte is precisely printed onto the titanium layer before the second electrode is added. This removes the need for both hole-drilling and additional sealing, and reduces the amount of electrolyte required.

Beyond developing this new method, the researchers then compared the performance of the hole-free DSSC to a reference device, under full sun light intensity. The efficiency of the printed cell was found to be 6% higher than that of the reference (two-hole) cell. And significantly, the printed cell had a lower overall resistance, and maintained 100% of its performance over 1120 hours in an accelerated ageing test. These results surprised the researchers, as their main motivation was to make DSSC fabrication easier and quicker. The next step will be to determine the exact mechanism behind the improved performance.

The team say that these results will accelerate the “production of cheaper, more robust, large area DSSC solar panels.” We’ll have to wait and see.

S.G. Hashmi, M. Ozkan, J. Halme, K.D. Misic, S.M. Zakeeruddin, J. Paltakari, M. Grätzel, P.D Lund - “High performance dye-sensitized solar cells with inkjet-printed ionic liquid electrolyte.” Nano Energy (2015) 17, 206-215. DOI: 10.1016/j.nanoen.2015.08.019