The rare metal Ruthenium used in conventional DSSCs is also extensively used in the electronics industry. Recently there have been issues with supply due to problems experienced in South African mines as a result of the power crisis suffered last year by state power utility Eskom. Whilst demand has decreased with build-up of stocks in the hard disk industry and an increase in recycling, experts believe the white metal may see a rise in demand over the longer term as new users are attracted by lower prices.
A new high-performance dye-sensitized solar cell (DSSC) has been developed that does not use Ruthenium by research scientists Kohjiro Hara and Nagatoshi Koumura at AIST.
The new cell contains a new organic dye photo absorption material (MK-2) as an alternative to the ruthenium complex and also a new organic dye solar cell using a gelator with an organic electrolyte oligomer structure. This means the cell can be manufactured at low cost due to its easy preparation and low-priced materials.
The dye was optimized with the aid of molecular design technology. Although coumarin dyes provided high efficiencies of up to 8% using volatile organic solvent based electrolyte, the efficiency of electron transfer from the dye to the titanium oxide electrodes was lower and the electron life was shorter, decreasing the solar-cell performance. Consequently, an MK dye (carbazole dye) was synthesized to solve this problem.
In addition, the use of ionic liquid (IL)-based electrolyte in the cell has led to a good long-term stability of more than 2000 hours under AM 1.5 G irradiation (100 mW cm-2), compared to 100 hours in DSSCs with volatile organic solvent based electrolytes.
Furthermore this DSSC achieved a high solar-to-electricity conversion efficiency (cell efficiency) of 7.6% under AM 1.5 G irradiation, which is one of the highest performances among DSSCs with IL based electrolytes, and 5.5% efficiency with ionic gel-based electrolyte.
The researchers aim to attain 18% cell efficiency and 15% module efficiency - equivalent to the efficiency of crystalline silicon with the aim of early commercialization for indoor application.
For more attend Photovoltaics Beyond Conventional Silicon Europe.
Top image: Organic-dye-sensitized solar cell prototype (Source: AIST).