Silicon has always been the material of choice for solar cell technology because of its low cost, stability and efficiency. The unfortunate news is that silicon solar cells are rapidly approaching their theoretical limits. However, pairing them with other materials may Help to break the upper limit.
Now, researchers at the EPFL and the Swiss Centre for Electronics and Microtechnology (CSEM) have developed a new combination of silicon and perovskite solar cells, as mentioned in their research report. The cell's laboratory efficiency has exceeded the 25.2% efficiency record - a new record for this solar cell combination technology.
At present, the efficiency of silicon solar cells on the market is up to 20% to 22%, which is not bad, but it does not make the technology have more room for development. In recent years, perovskite is an ideal substitute, Efficiency has increased from 3.8% in 2009 to more than 20% in 2016. However, because its price is more expensive than ordinary silicon solar cells, and has its own efficiency ceiling, the degree of commercialization is not high.
The use of perovskites and silicon in a solar cell may help to take advantage of both materials. Perovskites are better at converting green and blue light into electricity, while silicon is dedicated to red and infrared light. So they can capture a wider spectral range.
Research authors Florent Sahli and Jérémie Werner said that by combining these two materials, the solar spectrum can be maximized and the amount of electricity generated can be maximized. The calculations and work done in the current study show that 30% should be achieved very quickly. effectiveness.
The team's new silicon-perovskite solar cell has achieved an efficiency of 25.2%. This exceeds the series of solar cells that were developed in 2015 by monocrystalline silicon solar cells and perovskite solar cells. Its efficiency is only 13.7%.
The main obstacles of these tandem cells are in the manufacturing process. Usually, perovskites are deposited as liquid on the surface, but the texture of the silicon makes it difficult. The surface of the silicon cell consists of a large number of 'pyramid' structures of about five microns high. This structure can better capture and absorb light.
Sahli said that by now, the standard method for making perovskite/silicon tandem cells is to flatten the 'pyramid' of the silicon cell, but this will reduce its optical properties and thus its performance. After that, the perovskite cell will be deposited. At the top of this step, the steps of the manufacturing process are also added.
In this study, scientists first used evaporation to create an inorganic base layer covering the 'pyramid'. Then, a liquid organic solution was added by spin coating, which penetrated into the pores of the base layer. Finally, the team heated the substrate to 150 ° C ( 302 °F), so that the perovskite will crystallize at the top to form a film covering the entire surface of the silicon.
The researchers say the process is relatively simple and can be integrated into existing production lines in just a few extra steps. This will help with new tandem cell production without overcosting.
