Researchers from Helmholtz-Zentrum Berlin (HZB) increased the efficiency of perovskite-silicon tandem solar cells
Tandem solar cells made of silicon and metal halide perovskite compounds are capable of converting a large amount of solar spectrum into electricity. However, some amount of the light is reflected, which reduces the efficiency of energy conversion. Nanostructures can help to significantly reduce the refection, which leads to more absorption of light by solar cells. Now, a team of researchers led by Steve Albrecht, a HZB physicist, found an alternative approach of light management with textures in tandem solar cells. The team succeeded in developing an efficient perovskite/silicon tandem device, with a silicon layer that was etched on the back-side. The perovskite layer can be used by spin-coating onto the smooth front-side of the silicon. A polymer Light Management (LM) foil was later applied to the front-side of the device for a high-quality perovskite film processing on a flat surface. According to the researcher, the approach enabled to considerably improve efficiency of a monolithic perovskite-silicon heterojunction tandem cell from 23.4 % to 25.5 %.
Moreover, the team developed a complex numerical model for complex 3D features and their interaction with light. This allowed to measure the efficiency of perovskite-silicon tandem solar cells with textures at various interfaces. The complex simulations and empirical data revealed that an efficiency of 32.5 % can realistically be achieved when high quality perovskites can be incorporated with a band gap of 1.66 eV. Moreover, the real-time weather data allowed to measure the energy yield of different cell designs at three different locations for over the course of a year. The simulations demonstrated that the LM foil on the front-side of the solar cell device performs efficiently under diffused light irradiation. The researchers stated that tandem solar cells with the new LM foil can be preferred for incorporation in building-integrated photovoltaics (BIPV). The research was published in the journal Energy & Environmental Science on October 25, 2018.