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New record! new technology! Solar cell efficiency will exceed 30%
- Sep 20, 2018 -

After decades of large-scale investment, silicon solar cells have occupied 90% of the photovoltaic market, but they are close to their theoretical limit efficiency. In order for solar costs to continue to fall, more innovative materials are needed.



Recently, researchers at the EPFL and the Swiss Centre for Electronics and Microtechnology (CSEM) have developed a new combination of silicon and perovskite solar cells and reported a 25.2% efficiency record - this This is a new record in this solar cell combination technology, published in the journal Nature Materials.


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The current efficiency of silicon solar cells on the market is up to 20% to 22%, which is not bad, but does not allow the technology to have more room for development. In recent years, perovskite has been an ideal alternative, with efficiency increasing from 3.8% in 2009 to more than 20% in 2016. Despite this, it is more expensive than ordinary silicon solar cells and has its own upper limit of efficiency.


The use of perovskites and silicon in a solar cell may help to take advantage of both materials. Perovskites perform better in converting green and blue light into electrical energy, while silicon is dedicated to red and infrared light, so they can capture a wider spectral range.


“By combining these two materials, we can make the most of the solar spectrum and increase the amount of electricity generated,” said study authors Florent Sahli and Jérémie Werner. “The calculations and work we have done show that 30% efficiency should be achieved soon.”


The team's new silicon-perovskite solar cell has achieved an efficiency of 25.2%. This exceeds the series-connected solar cells that were developed in 2015 and consisted of a monocrystalline silicon solar cell and a perovskite solar cell. The efficiency is only 13.7%. The main obstacle to these series batteries is in the manufacturing process. Usually, perovskites will deposit as a liquid on the surface, but the texture of the silicon makes it difficult. It consists of a large number of "pyramid" structures of about five microns high to better capture and absorb light.

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“The standard way to make perovskite/silicon tandem cells is to flatten the 'pyramid' of silicon cells, but this will reduce its optical performance and therefore its performance, and then deposit the perovskite cell, Sahli said. At the top, it also adds steps to the manufacturing process."


In this study, scientists first used evaporation to create an inorganic base layer that covered the 'pyramid'. Then, a liquid organic solution is added by spin coating, which penetrates into the pores of the base layer. Finally, the team heated the substrate to 150 ° C (302 ° F) so that the perovskite crystallized 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 the new series battery production without the cost being too high, and the manufacturer does not need to build a new plant, just update the existing silicon cell production line.