By layering two different mineral forms of titanium oxide on perovskite, scientists in Japan have improved the efficiency of pervoskite-based solar cells by almost 17 percent.
AsianScientist (Mar. 11, 2019) – Researchers in Japan have layered different mineral forms of titanium oxide on top of one another to improve perovskite-type solar cell efficiency. Their findings are published in the journal Nano Letters. While most solar cells are made of silicon, such cells are difficult to manufacture, requiring vacuum chambers and temperatures above 1,000°C. Research efforts have therefore recently focused on a new type of solar cell based on metal halide perovskites. Perovskite solutions can be inexpensively printed to create more efficient, inexpensive solar cells. Perovskites can turn light into electricity, but they have to be sandwiched between a negative and positive electrode. One of these electrodes has to be transparent to allow the sun’s light to reach the perovskites. Not only that, any other materials used to help charges flow from the perovskites to the electrode must also be transparent. In this study, researchers led by Associate Professor Koji Tomita of Kanazawa University, Japan, explored the effect of using electron transport layers made of anatase and brookite, different mineral forms of titanium oxide, in perovskite-based solar cells. The anatase layers were fabricated by spraying solutions onto glass coated with a transparent electrode that was heated to 450°C. Meanwhile, the researchers used water-soluble brookite nanoparticles to create the brookite layers, noting that water-soluble inks are more environmentally friendly than conventional inks. “By layering brookite on top of anatase we were able to improve solar cell efficiency by up to 16.82 percent,” said Tomita. These results open up a new way to optimize perovskite solar cells, namely via the controlled stacking and manipulation of the different mineral forms of titanium oxide. The researchers added that the use of different mineral phases and combinations of these phases allows for better control of the electron transport out of the perovskite layer, also stopping charges from recombining at the border between the perovskite material and the electron transport layer. The researchers hope that their findings will facilitate the development of a new generation of printable, low-cost solar cells that could provide affordable clean energy in the future.