Using micro-structured layers, a HZB device could increase the efficiency of perovskite-silicon tandem solar cells, resulting in 25.5 percent, which is the highest value published to date. The team used computational simulations to investigate the conversion of light into several devices with different nanostructured surfaces. This allowed optimizing light management and analyzing energy performance in detail. The study has already been published in Energy and environmental sciences.
Tandem solar cells made from silicon peroxide compounds and metal halide can turn a particularly large part of the solar spectrum into electrical energy. However, part of the light is reflected and lost to the effects of energy conversion. Using nanostructures, the reflection can be significantly reduced so that the solar cell can capture more light. For example, the pyramid-shaped microfeatures can be recorded in silicon. However, these characteristics cause microscopic roughness on the silicon surface, which is no longer suitable as a substrate for the deposition of extremely thin layers of perovskite. This is because Perovskites tend to be deposited in a polished wafer using the processing of solutions to form an extremely thin film, much thinner than the pyramidal characteristics. A layer of asphyxiated silicon surface therefore prevents the formation of a layer of uniform conformation.
Efficiency improved from 23.4 percent to 25.5 percent
A team led by HZB physicist Steve Albrecht investigated an alternative approach to light management with textures in tandem solar cells. The team manufactured an efficient perovskite / silicon tandem device whose silicon layer was engraved on the back. The perovskite layer could be applied by spincoating on the smooth front of silicon. Subsequently, the equipment applied a polymer light management sheet (LM) to the front of the device. This allowed to process a high quality perovskite film on a flat surface, although it benefits from the texture of the front. "In this way, we have been able to considerably improve the efficiency of a monolithic perovskite-silílico heterogeneous tandem cell of 23.4 percent to 25.5 percent," says Marko Jošt, first author of the post-doctorate study of the Albrecht team.
The numerical model shows the possibility of up to 32.5 percent
In addition, Jošt and colleagues developed a sophisticated numerical model for complex 3-D features and their interaction with light. This allowed the team to calculate how the different designs of devices with textures on various interfaces affect efficiency. "Based on these complex simulations and empirical data, we believe that an efficiency of 32.5 percent can be achieved realistically-if we succeed in incorporating high quality perovskites with a band separation of 1.66 eV," says Jošt.
Suitable for the construction of integrated PV
Team leader Steve Albrecht adds: "Based on real weather data, we could calculate energy performance over a year – for different cell designs and for three different locations." In addition, the simulations show that the LM leaf on the front of the mobile device is particularly advantageous under the irradiation of diffused light, that is, not just under the perpendicularly incident light. The Tandem solar cells with the new LM sheet could also be suitable for incorporation into the integrated photovoltaic building (BIPV), opening large and new areas for power generation from large facades of skyscrapers.
Perovskite touch pad / CIGS with 24.6 percent record efficiency
Marko Jošt et al, Textured interfaces in perovskite / tandem silicone monovyte solar cells: advanced light management for better efficiency and energy performance, Energy and environmental sciences (2018). DOI: 10.1039 / C8EE02469C
Helmholtz Association of German Research Centers
New records in perovskite-silicon tandem solar cells through better light management (2018, November 13)
recovered on November 13, 2018
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