Scientists at Stanford University have developed a new thin-film solar cell that combines plasma to improve performance and economic viability.
Plasma (Plasmonics) is a new branch of science and technology that involves the interaction between light and metal.
Under certain conditions, these interactions produce a high frequency and high density of waves. This electronic pulse walks in the form of abnormally large and small densities similar to the movement of sound in the air.
Mike McGehee, associate professor of materials science and engineering at Stanford University, led a multidisciplinary team of engineers that use plasma to help thin-film solar cells capture light sources with greater efficiency.
Essentially, the team printed a honeycomb pattern of nanoscale dimples in the metal layer of the solar cell. The basic structure is similar to a nanometer square. With bumps, scientists have measured nano-dots called 300 nm in diameter and 200 nm in height on imprinted materials.
In order to achieve this structure, scientists applied a thin layer of paste on a transparent conductive base. The batter consists of titanium dioxide, a light-transmitting, semi-porous metal.
They used nanometric square irons to imprint nano-marks on the batter and added a layer of photosensitizing dye into the dimples and pores in the squares. Finally, they added a finishing silver coating.
This bumpy silver layer offers two main benefits. First, it can act as a mirror and initiate the second round of integration. Second, the light interacts with silver nanodots to produce a plasma effect.
According to the design, photons will enter and pass through the transparent base and titanium dioxide layer. Some of the photons will then be absorbed by the light-sensitive dye to generate the current.
At the same time, the remaining photons will come into contact with the reflected silver. This will extradite them back to the solar cell for the second round of collection. However, some photons that strike silver will strike the nano-dots and also cause plasma waves to flow outward.
Advantages and limitations
"Using plasma, we can absorb light in thinner films like never before," explains Mr. McGee.
"The thinner the thin film, the closer the electrical particles are to the electrode. In essence, it can make more electrons go to the electrode and become electricity," he added.
According to the researchers, the use of flexible solar cells for photosensitizing dyes to generate electricity brings many benefits, including cost and energy efficiency.
However, dye-sensitized solar cells suffer from the inefficiency of converting light into electricity. The best thin-film solar cells are only about 8% efficient, converting light energy into electricity, far less than the bulky commercial technology that has reached 25% efficiency.
In addition, the estimated lifetime of solar films is only about 7 years, which is much lower than the commercial standard of 20 to 30 years.
Nevertheless, Mr. McGee believes that increasing the efficiency to 15% and lifespan to 10 years will allow the commercialization of thin film solar cells.