Solar, Storage

Tanaka to sell 11.4%-efficient dye-sensitized cells using recycled Ru

Japan’s Tanaka Kikinzoku Kogyo says it will market a new dye-sensitized solar cell with conversion efficiency exceeding 11.4%, among the highest levels for DSSCs, and plans to keep costs low using a mostly recycled key material.

December 29, 2011 – Japan’s Tanaka Kikinzoku Kogyo says it will market a new dye-sensitized solar cell with conversion efficiency exceeding 11.4%, among the highest levels for DSSCs, and plans to keep costs low using a mostly recycled key material.

Generally speaking, dye-sensitized solar cells involve a dye sandwiched between two electrodes, with an electrolyte catalyst on one end (acting as a cathode) and a thin layer on the other (e.g. TiO2 particles, acting as an anode). Light is shined upon and absorbed by the dye, which separates charges at the catalyst/layer interfaces to create electrical current (see image below). Conversion efficiency is typically in the realm of thin-film solar constructions, well below silicon-based solar PV, but with the promise of much simpler and less costly manufacturing and application — e.g. flexible using plastic substrates, and even in colors.

In this case, Taiwan’s National Central University has developed a ruthenium complex dye, CYC-B11, that they say “exhibits the capacity” to better absorb sunlight, topping 11.4% conversion efficiency, evaluated at Switzerland’s EPFL. (More on the technology was published in ACS Nano in Sept. 2009.) Tanaka has licensed a version of the dye that’s rated at ~9.5% conversion efficiency, and the company says it is working on ways to improve manufacturing process yields, and recycling Ru metal to lower the dye cost. (The Nikkei daily reports that the company is investing ¥300M to set up a facility at its plant in Tsukuba, Ibaraki Prefecture, to make 1 metric ton/year of the pigment; and that plans to use 95%-recycled Ru will keep the price down below ¥10,000/gram.) Tanaka aims to push annual sales of the Ru complex dyes to ¥300M by 2015, alongside estimates that DSSC use will top 5%-10% of the overall solar cell market.

 

Power generation architecture of a dye-sensitized solar cell. (Source: Japancorp, Tanaka)