Maximizing Current Density in Monolithic Perovskite Silicon Tandem Solar Cells

Perovskite silicon tandem solar cells can overcome the efficiency limit of silicon single-junction solar cells. In two-terminal perovskite silicon tandem solar cells, current matching of subcells is an important requirement. Herein, a current-matched tandem solar cell using a planar front/ rear side-textured silicon heterojunction bottom solar cell with a p-i-n perovskite top solar cell that yields a high certified short-circuit current density of 19.6 mA cm-2 is reported. Measures taken to improve the device are guided by optical simulation and a derived optical roadmap toward maximized tandem current density. To realize current matching of the two subcells, variation of the perovskite bandgap from ≈1.68 to 1.64 eV and thickness is investigated. Spectrometric characterization, in which current-voltage curves of tandem devices are recorded at systematically varied spectral irradiance conditions, is applied to determine the current matching point. In addition, remaining device limitations such as nonradiative recombination at the perovskite's interfaces are analyzed. Replacing the hole transport layer PTAA by 2PACz results in an overall certified power conversion efficiency of up to 26.8%. Precise simulation based on the device structure is essential as it provides efficient paths toward improving the device efficiency.