Silicon film solar cell conversion rate world record is refreshed

Stable photoelectric conversion efficiency up to 13.6%

A research team composed of researchers from various Japanese institutions recently announced that they have developed a three-junction thin-film silicon solar cell with a stable conversion efficiency of 13.6%, which successfully broke the previously reported world record of 13.44%. The researchers said that if some rationalization improvements are made, the efficiency can reach more than 14%. Related papers were published in the Journal of Applied Physics Letters.

The research team consists of people from Japan's largest research centers, including the Advanced Institute of Industrial Science and Technology (AIST), Photovoltaic Power Technology Research Association (PVTEC), Sharp, Panasonic and Mitsubishi.

AIST researcher Sato Tamura said that the new research has achieved two important results. One is to develop a thin-film silicon solar cell with advanced light-capturing capability; the other is to achieve a photocurrent density of 34.1 mA per square centimeter on a microcrystalline absorption layer of only 4 microns thick.

There are many different types of solar cell efficiencies, and it is often difficult to make direct comparisons between different types of efficiencies. This study used a stable photoelectric conversion efficiency (PCE).

Sato Tamura pointed out that as long as the solar cells are exposed to light, humidity, temperature and other conditions, the conversion efficiency will be a certain degree of attenuation, so most solar cells are evaluated by "initial" efficiency. If the battery is a material such as crystalline silicon, the performance is relatively stable; if amorphous silicon, that is, amorphous silicon, is involved, the situation will be completely different, and its conductivity will be significantly degraded after exposure. This property is called SWE. effect.

Many factors can lead to photoinduced degradation of silicon solar cells. One countermeasure is to use a honeycomb structure on the substrate. Previously, honeycomb textures were mostly used in single junction solar cells, which were made of only one semiconductor material and absorbed only one wavelength of light. In the new study, scientists have found that this structure can also be used in multi-junction solar cells, which can absorb multiple wavelengths of light and have better trapping performance than single-junction cells. To further improve efficiency, they also fine-tuned the honeycomb texture and added an anti-reflection film with a moth-eye structure.

To make a fair comparison, the researchers tested solar cells exposed to the sun for some time. The results show that the initial efficiency of the battery can reach 14.5%, and the stability efficiency is also 13.6%.

Despite refreshing a new record, the researchers believe that there is still much room for improvement in the battery. After improving the performance of the top layer of the solar cell and solving the spectral mismatch problem, its stability efficiency is expected to exceed 14%.