Near-infrared optical losses induced by rear contacts in four-terminal perovskite/silicon tandem solar cells

Four-terminal (4T) perovskite/silicon tandem solar cells offer a promising architecture to surpass the theoretical efficiency limits of single-junction photovoltaics; however, achieving high performance requires simultaneously optimizing top cell efficiency and sub-bandgap photon transmission. This study presents an experimental and computational deconvolution of near-infrared (NIR) optical losses in 4T tandem devices. Experimental characterization demonstrates that integrating a commercial silicon bottom cell (15.60%) beneath a perovskite top cell with a conventional silver (Ag) rear electrode drastically suppresses the bottom cell short-circuit current density ( J SC_EQE ) from 37.85 to 1.18 mAcm − 2 . This 89.7% loss in NIR photon harvesting stems primarily from metallic opacity and parasitic plasmonic absorption. Replacing the Ag layer with a semi-transparent perovskite top cell restores the bottom cell ( J SC_EQE ) to 11.46 mAcm − 2 , achieving a cumulative tandem efficiency of 15.90% alongside an optimized 11.18% (top cell). To eliminate remaining optical shielding, Monte Carlo Wafer Ray Tracer simulations and admittance analysis reveal that a 70 nm indium tin oxide (ITO) rear contact provides an optimal phase shift \(\:({φ})\) at 1000 nm while maintaining minimal free-carrier absorption (4.49%). This computationally optimized transparent conductive oxide recovers the bottom cell J SC_WRT to 19.73 mAcm − 2 , projecting a total 4T tandem efficiency of 19.82%.