Dye-sensitized solar cells with carbon nanotube transparent electrodes offer significant cost savings

Mar 15, 2012
Carbon nanotube electrodes. The use of carbon nanotubes has a significant cost advantage. However, in earlier designs (left), the carbon nanotubes degraded through chemical processes (e-: electrons, I3-: ions in the liquid). Using a thin protective layer of titanium oxide now stabilizes the nanotubes (right), increasing the performance of these cells. Credit: 2011 AIP

Solar energy is one of the most promising forms of renewable energy, but the high cost of conventional solar cells has so far limited its popularity. To increase the competitiveness of solar energy, scientists have turned to the development of dye-sensitized solar cells — solar cells that use low-cost organic dyes and titanium dioxide (TiO2) nanoparticles in place of expensive semiconductor and rare earth elements to absorb sunlight. Zhaohong Huang at the A*STAR Institute of Materials Research and Engineering and co-workers have now reduced the cost of dye-sensitized solar cells even further by replacing indium tin oxide (ITO) — the standard material for transparent electrodes — with carbon nanotubes.

A typical dye-sensitized solar cell comprises a porous layer of TiO2 nanoparticles immersed in an organic dye. The dye absorbs the sunlight and converts the energy into electricity, which flows into the TiO2 nanoparticles. The sun-facing side of the solar cell is usually covered with a transparent electrode that carries the charge carriers away from the TiO2 and out of the solar cell. “Unfortunately, ITO electrodes are brittle and crack easily,” says Huang. “They are also expensive and could incur up to 60% of the total cost of the dye-sensitized solar cell.”

Huang and his team therefore replaced the ITO electrode with a thin film of carbon nanotubes. Carbon nanotubes conduct electricity and are almost transparent, flexible and strong, which make them the ideal material for transparent electrodes. The only drawback is that photo-generated charge carriers in the nanotube may recombine with ions in the dye, which reduces the power conversion efficiency of the solar cell.

To overcome this problem, Huang and his team placed a TiO2 thin film in between the thin film and the porous layer. They found that the performance of dye-sensitized with TiO2 thin film was significantly better than those without. However, they also found that the solar conversion efficiency of their new dye-sensitized solar cells was only 1.8%, which is lower than that of conventional solar cells using ITO electrodes. This is due to the higher electrical resistances and reduced optical transparency of the carbon nanotube films, which limits the amount of sunlight entering the cell.

“We are now studying different ways to enhance the conductivity and transparency of the films,” says Huang. “Furthermore, we are planning to replace the bottom platinum electrode with carbon nanotube thin film to reduce the cost of dye-sensitized solar cells further.”

If successful, the results could have a great impact on the cost and stability of dye-sensitized solar cells.

Explore further: Wiring up carbon-based electronics

More information: Research article in Applied Physics Letters.

Provided by Agency for Science, Technology and Research (A*STAR)

3.6 /5 (5 votes)
add to favorites email to friend print save as pdf

Related Stories

Dye-sensitized solar cells break a new record

Nov 14, 2011

(PhysOrg.com) -- Dye-sensitized Grätzel solar cells have just set a new efficiency benchmark. By changing the composition and color of the cells, an EPFL team has increased their efficiency to more than ...

Solar cells go thin and flimsy

Sep 04, 2006

The next generation of solar cells made out of plastics and microscopic crystals instead of silicon are taking shape at UQ (University of Queensland). UQ Master of Physics student Michael Deceglie is working ...

Affordable solar technology

Jan 06, 2011

An innovative Oxford company has developed new solar cell technology that is manufactured from cheap, abundant, non-toxic and non-corrosive materials and can be scaled to any volume.

Recommended for you

Thinnest feasible nano-membrane produced

14 hours ago

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

17 hours ago

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 0

More news stories

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

Leeches help save woman's ear after pit bull mauling

(HealthDay)—A pit bull attack in July 2013 left a 19-year-old woman with her left ear ripped from her head, leaving an open wound. After preserving the ear, the surgical team started with a reconnection ...

Six Nepalese dead, six missing in Everest avalanche

At least six Nepalese climbing guides have been killed and six others are missing after an avalanche struck Mount Everest early Friday in one of the deadliest accidents on the world's highest peak, officials ...