Japanese from Kaneka developed a solar cell with an efficiency of 26.3%
Alternative energy occupies a large market share in several countries in Europe and in the United States. Funds invest heavily in creation. As for solar cells, the amount of energy produced by them depends on the efficiency of conversion of solar energy into electrical energy. Scientific and commercial organizations for many years engaged in improving this indicator, and I must say, some developers succeed.
The theoretical limit of the efficiency of silicon photocells is 29%. Speaking of such a limit, it implies a "clean" photocell, concentrators and other additions. For modern commercial systems, 15-19% can be considered a very good indicator. Developers of Kaneka Corporation have a photocell efficiency of up to 26.3%, breaking the previous record of 25.6%.
Scientists who participated in the creation of these photovoltaic cells stated that they could increase the efficiency a little more, up to 26.6%, but this still needs some time for additional research.The result, declared by the Japanese, is confirmed by a special commission,.
Developers of a new type of photocell that the useful surface of the cell is 180.4 cm2. A thin-film heterojunction (contact of two different semiconductors) was used in the battery to minimize the so-called forbidden zones. These are regions of energy values that an electron cannot possess. Plus, the top layer of the battery was covered with amorphous silicon with an anti-reflective coating to minimize albedo and reduce photon scattering.
The network of electrodes was lowered from the surface of the cell to its “bottom”. Thus, the creators, according to them, managed to increase the amount of sunlight entering the cell while simultaneously reducing optical losses.
The developers, analyzing the energy loss in the new battery, were able to understand what prevents to achieve an efficiency of 29%, the theoretical limit for photovoltaic cells. A half percent loss, in relation to 29%, is the loss due to the resistance of the conductors, 1% is the loss of solar energy in the optical layer and 1.2% is the loss due to external recombination. These are the cases of the meeting of free electrons with positively charged holes with subsequent reunion with positive ions.
“There are a large number of materials, technical processes and types of photovoltaic architecture that can be used,” Kunta Yoshikawa, representative of the solar cell development team at Kaneka. “We achieved an efficiency of 26.3% thanks to the development of our own technology of chemical deposition of battery structural elements from the vapor state, work with the optical properties of the material and thin-film technology.”
This company has been developing thin-film solar cells since 1980. Kaneka has been working on photoelectric cells with heterojunction since 2009. “One of the key steps to create such photovoltaic cells is the use of chemical plasma deposition — a process that can be used in industry,” Yoshikawa said.
In his opinion, when creating a highly efficient photocell, it is necessary to observe a balance between such an important criterion as battery life, internal resistance and its optical properties. “Although it is quite possible to achieve outstanding results for one of these factors, it is extremely difficult to keep the balance of all three properties in one device,” the developers say.
Progress in the efficiency of photovoltaic cells from the 70s of the last century to our days
The Japanese managed to do this thanks to the use of a specific front panel architecture, which provides excellent optical properties and at the same time the life of the photocell. Plus, experts have achieved and reduce the internal resistance of the battery, although it was not easy.
Representatives of the company Kaneka declare that the technological process of creating such elements can be used at enterprises for the production of high efficiency solar cells in industrial quantities. The study was funded by NEDO (New Energy and Industrial Technology Development Organization). Now the developers, together with NEDO, plan to add the cost reduction of “solar” electricity to the level of $ 0.06 per kilowatt-hour by 2030.
A few years ago, Panasonic was also involved in increasing the efficiency of photocells. Developers of this company figure up to 25.6%. The surface area of the solar cell at Panasonic was 143.7 cm2. By the way, this team also used a thin-film heterojunction.