The efficiency of Perovskite/Si tandem solar cells depends on the location of deployment
Perovskite/silicon tandem solar cells are considered one of the most promising candidates for third-generation solar cells to surpass the Shockley-Queisser limit. We calculated the maximum power conversion efficiency of perovskite/silicon tandem solar cells under realistic outdoor illumination conditions. Our results suggest that different locations may benefit from different tandem solar cell combinations.
Tandem solar cells
Only 7 years after the first report of a perovskite solar cell their power conversion efficiency has already increased to more than 20%. In contrast, after 60 years of research, the power conversion efficiency of silicon solar cells seems to saturate close to its theoretical limit of 29%. To further improve the power conversion efficiency at affordable cost new strategies such as tandem cell configurations have to be applied.
A tandem solar cells consists of two or more individual sub cells which are optically coupled by absorbing different parts of the incident solar spectrum, allowing for a more efficient conversion of the broad-band solar spectrum to electricity. In case of a perovskite/silicon tandem solar cell the perovskite top cell absorbs the low-wavelength region while the transmitted high-wavelength region is absorbed by the silicon bottom cell. Multiple wiring schemes between the perovskite top cell and the silicon bottom cell have been proposed, including the conventional series tandem, the electrically independent four-terminal tandem, and tandem cells connected on a module level. For all those perovskite/silicon tandem solar cell configurations the limiting efficiency can be raised from 34 to 45%.
Location dependent efficiency limit
Efficiency calculations are typically performed using standard test condition (AM1.5G, 1 kW/m2, 25 °C). However, only a fraction of solar spectra and temperatures throughout a year correspond to such conditions. We calculated the efficiency limit of perovskite/silicon tandem solar cells using solar spectra and temperatures measured in two locations with distinctly different climate conditions, Utrecht in The Netherlands, and Denver, CO (US). Spectral changes turn out to be far more important than temperature changes over the course of the year. We find that the series connected cells are most stable against temperature changes, and that four-terminal tandems and tandem cells connected on a module level are most stable against spectral variations. Furthermore, we show that perovskite/silicon tandem solar cells are promising in all configurations even at non-ideal climate conditions.
Efficiency Limit of Perovskite/Si Tandem Solar Cells
M.H. Futscher, B. Ehrler, ACS Energy Lett., 2016, 1 (4), pp 863–868