Solar Efficiency

In the November 20th blog titled Engineering Solar: Photovoltaic Cells we looked at the current state of solar cells and the advances in the solar energy field. At the time silicone was one of the most abundant semiconductor materials available and was used in the majority of solar cells. Thin wafers of silicone were given a treatment that created a positive electric field on one side and a negative field on the other. As the sun makes contact with the silicone’s surface the electrons within it separate from the atoms and begin to travel through the cell. By placing conductive leads on either side of the solar cells the electricity that is generated can then be collected and reused. A solar panel is created by combining a large amount of these cells into what are called solar modules and then combining modules into a panel. When placed together in great numbers these cells have the ability to generate a large amount of usable energy.

New Material Approach

In a recent publication by Lane Martin, a professor of materials science and engineering at Illinois, he claimed that his research created “a fundamentally new way of approaching and

[more efficiently utilizing the solar spectrum]”i By combining aspects of condensed matter physics, semiconductor device engineering, and photochemistry Martin’s group designed a new photocatalyst that replaces the silicone base with TiO2 (titanium dioxide) along with a variety of other oxides that enhance absorption of visible light which in turn leads to more efficient utilization of the solar spectrum.ii This new material overcomes the main obstacle in current solar panels which is that they poorly absorb visible light because they are known as wide band gap materials. TiO2 has high chemical stability, is non-toxic, is normally fairly inexpensive and has a very large band gap alignment. One of the materials that is paired with TiO2 is SrRuO3 which is known for its unusual electronic structure, which unexpectedly led to high absorption across the entire visible spectrum and reflected very little of the light energy that it came in contact with. SrRuO3 is a very complicated substance to profile because of its unique properties. It possesses metallic-like temperature dependence of its resistivity and ferromagnetism as well as its ability to be used as a conducting electrode in oxide heterostructures.iii This material cannot be called a metal though because its electron structures are a combination of complex electronic density states and electron correlations.

Future of Solar Panel Technology

The long term application for all solar panels, especially these new high efficiency versions, is to help ruduce our dependency on fossil fuels and move toward a more self sustainable and environmental society. With previous solar panels reaching a maximum efficiency of about 20%, it was not feasible to use them to fuel everyday needs that require large amounts of energy to operate such as vehicles and buildings. While these new solar panels may not be ready for that challenge, they can reach a much higher level of efficiency by producing nearly 100mW/cm2 of energy.iv These new advances in renewable energy technology is paving the way for solar panels to be a primary source for energy on day. As we have discussed in previous blogs, clean renewable enegy comes in many different forms such as hydro and wind as well as solar and look forward to blogging about the tenological and engineering advances as they present themselves.

iScience Daily “New Material Approach Should Increase Solar Cell Efficiency” April 23, 2013

ii Kubetz, Rick Nanotech Now “New Material Approach Should Increase Solar Cell Efficiency” April 23, 2013 

iii Kubetz, Rick PhysOrg “New Material Approach Should Increase Solar Cell Efficiency” April 23, 2013

iv Kubetz, Rick PhysOrg “New Material Approach Should Increase Solar Cell Efficiency” April 23, 2013