EU PVSEC Programme Online
EU PVSEC 2021, 6 - 10 September 2021
Presentation: 3AO.5.5 Periodic Nanostructures for High-Efficient Perovskite/Silicon Tandem Solar Cells
Type: Oral
Date: Monday, 6th September 2021
15:15 - 16:45
Author(s): J. Sutter, P. Tockhorn, P. Wagner, K. Jäger, A. Al-Ashouri, B. Stannowski, S. Albrecht, C. Becker
Presenter / Speaker: J. Sutter, HZB, Berlin, Germany
Event: Conference Conference
Session: 3AO.5 Tandem Solar Cells Process and Performance
Topic: 3. 5 Tandems
Summary / Abstract: In just about a decade of research metal halide perovskites have led to highly efficient thinfilm solar cells and present a suitable tandem solar cell partner for established silicon photovoltaics. Further increase of power conversion efficiencies (PCEs) is expected to be achieved with adequate light management. In silicon solar cells, potassium hydroxide etched random pyramid structures are commonly used as light-management structure with several micron structure height. However, these pyramids are difficult to apply in a tandem configuration since the commonly used solution-based deposition techniques of the perovskite absorber films are not easily compatible with these large structure sizes. In this work, we report on monolithic perovskite/silicon tandem solar cells comprising tailored nanostructures for advanced light management, which are compatible with spin-coating of perovskite and enable PCEs exceeding 26%. A sinusoidal nanostructure with a structure period of 750 nm and an aspect ratio of approximately 0.5 was used. The structure was transferred into a crystalline silicon wafer combining nanoimprint lithography and reactive ion etching (RIE). A subsequent wet chemical defect etching step was implemented to mitigate the reduction of electronic quality due to the ingress of impurities in the RIE step. Perovskite top cells were deposited onto these nanostructured silicon bottom cells by spin-coating. The nanostructures of the buried interface were fully covered by the perovskite film leading to a flat perovskite surface. Perovskite/silicon tandem solar cells comprising these nanostructures yielded a steady-state PCE of 27.3%, short circuit current densities of 20.0 mA cm-2 , an open circuit voltage of 1.76 V, and a fill factor of 77.7%. Reflection losses in the near infrared wavelength regime of the sinusoidally structured device were reduced compared to its planar reference showing a potential in current gain of about 0.6 mA cm-2 . Analyzing the absolute photoluminescence signal, we could show a similar quasi-Fermi level splitting of the perovskite top absorber for the nanostructured tandem device compared to a planar reference. The herein presented light management nanostructures show the potential to boost the PCE of perovskite/silicon tandem solar cells to values close to 30%.