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U.S. Media: Research Says New Solar Cells Can Be Free From Cell Phone Charging Troubles
- May 02, 2018 -

U.S. Media: Research says new solar cells can be free from cell phone charging troubles

      US media said, imagine it, no longer have to charge mobile phones, e-readers, tablet PCs!

According to the report of the US "Science" Weekly website on April 23, researchers reported that they invented an extremely efficient solar cell that can use indoor and cloudy outdoor scattered light to generate electricity. Using this type of solar cell, one day it may be possible to develop a device that can be continuously charged and no need to plug it in again.

      It is reported that scattered light solar cells are nothing new, but the best scattered light solar cells require the use of expensive semiconductors. In 1991, Michael Gretzzel, a chemist at the Federal Polytechnic University in Lausanne, invented the so-called dye-sensitized solar cell, which works best under low light and is cheaper than a standard semiconductor battery. But under strong sunlight, the best-quality dye-sensitized solar cells can only convert 14% of the solar energy into electricity. In contrast, standard solar cells can convert 24% of solar energy into electricity. The reason why this happens is because the energy comes too fast and exceeds the processing capacity of dye-sensitized solar cells. But when energy arrives at a slower speed, such as the scattered light in a room, Gretzel's dye-sensitized solar cells can convert 28% of the light energy into electricity.

      It is reported that the working principle of dye-sensitized solar cells is slightly different from that of standard silicon solar cells. In a standard silicon solar cell, solar energy absorbed by the cell will kick electrons in silicon atoms to a higher energy level, enabling them to cross adjacent atoms and move to positively charged electrodes. Then they are collected there and shunted into the circuit. What is strange is that the vacancies left after the electrons leave the atom can also be moved. Over time, these vacancies move to negatively charged electrodes where they are filled with electrons from an external circuit. This process allows the silicon atom charge in the solar cell to be rebalanced so that electricity can be generated continuously.

      However, dye-sensitized solar cells differ. This battery also has two electrodes that collect negative and positive charges, respectively, but in the middle of the cell, there is a different kind of electronic conductor, usually some titanium dioxide particles, in addition to silicon. However, titanium dioxide absorbs light weakly. Therefore, researchers coated the surface of these titanium dioxide particles with organic dye molecules with excellent light absorption capabilities. The absorbed photons activate the electrons and vacancies on these dye molecules just as they do in silicon. The dye immediately transfers the activated electrons to the titanium dioxide particles, which are then transferred to the positive electrode. At the same time, vacancies are transferred to the negative electrode in the electrolyte that conducts the charge.

      The problem with dye-sensitized solar cells is that the vacancy moves less quickly in the electrolyte, causing the vacancy to accumulate near the dye and titanium dioxide particles. If an activated electron encounters an empty space, they will combine and release heat instead of electricity.

      The report said that in order to solve this problem, researchers have tried to dilute the electrolyte so that the vacancy can reach the target quickly. However, as long as the slightly diluted electrolytic solution is not perfect, it will lead to a short circuit, and the entire solar cell will be scrapped.

      Now, Gretzer and his colleagues have found a possible solution. They designed a combination of a dye and a molecule capable of conducting vacancies and made them tightly coated on the titanium dioxide particles, creating a perfect coating without any defects. This means that a slow moving space requires only a short distance to reach the negative pole. At the same time, they also reported that this compact coating has also increased the efficiency of scattered light utilization by dye-sensitized solar cells to 32%, close to the maximum theoretical value.

      Michael Vasilevski, a chemist at Northwestern University in the United States, said: "This is a truly remarkable improvement." Although the new device can only convert 13.1% of direct sunlight into electricity, the tile Silevsky pointed out that since the utilization efficiency of scattered light has increased by nearly 20%, it is hopeful to find new ways to improve the efficiency of the device under direct sunlight.

      According to reports, because the cost of dye-sensitized solar cells is much lower than that of silicon solar cells, if they can achieve near-silicon solar cell efficiency at a lower cost, it will be a success. Before this day comes, dye-sensitized solar cells can at least help us charge a lot of devices without wires, plugs, and external power supplies.