Subcell Operation and Long-Term Stability Analysis of Perovskite-Based Tandem Solar Cells Using a Bichromatic Light Emitting Diode Light Source

In monolithic tandem solar cells, current-voltage (J-V) characteristics of subcells provide invaluable information about their quality and tandem operation. However, accessing the subcell J-Vs is challenging and requires sophisticated spectral methods. Herein, a customized, bichromatic light emitting diode setup (BCLED) for in-depth analysis of tandem solar cells, suitable for subcell operation analysis, and long-term stability testing is presented. For this, two spectrally independent LED arrays are used to selectively bias the two subcells. The power of the developed setup is demonstrated by successfully disentangling the tandem J-V curve into subcell J-V curves. The method is based on a one-diode model for each subcell and is validated by electrical simulations. Afterward, it is used on a fabricated 27.6% efficient perovskite/silicon tandem device, resulting in great agreement with the measured J-V curve. Therefore, the BCLED setup is a versatile tool, suitable for subcell characteristics and long-term stability analysis of tandem solar cells.