From the past couple of years, the high-power conversion efficiency (PCE) of >25% and low-cost fabrication of single-junction perovskite photovoltaic cells have gained great attention from researchers. The bandgap tunability of these solar cells makes them an attractive and ideal candidate for tandem solar cell applications. The PCEs above than the single-junction solar cells theoretical Shockley-Queisser (SQ) radiative efficiency limit (31%-33%) can be achieved by harvesting a wide fraction of solar spectrum using multi-junction solar cells. In perovskite tandem (double-junction) solar cells, a wide-bandgap perovskite top cell is combined with either narrow-bandgap bottom cells of dissimilar materials like silicon (Si) and copper indium gallium selenide (CIGS) or with low bandgap perovskite solar cell. In this work, we have simulated perovskite/Si (PVK/Si), perovskite/CIGS (PVK/CIGS) and perovskite/perovskite (PVK/PVK) tandem solar cells and estimated 28.73%, 20.31% and 26.06% PCEs. The highest conversion efficiency is shown by PVK/Si tandem cells among others because of the suitable bandgap for tandem applications. Our work will guide the researchers for obtaining ultra-high conversion efficiency solar cells.
Saddam Hussain: US.Pakistan center for advanced studies in energy (USPCAS-E), University of engineering and technology (UET) Peshawar, Pakistan.
Adnan Daud Khan: US.Pakistan center for advanced studies in energy (USPCAS-E), University of engineering and technology (UET) Peshawar, Pakistan.
Saddam Hussain and Adnan Daud Khan Device Modeling and Numerical Characterization of Perovskite/Si Perovskite/CIGS and all-Perovskite
 J.-P. Correa-Baena et al., “Promises and challenges of perovskite solar cells,” Science (80-. )., vol. 358, no. 6364, pp. 739–744, 2017.
 T. Leijtens, K. A. Bush, R. Prasanna, and M. D. McGehee, “Opportunities and challenges for tandem solar cells using metal halide perovskite semiconductors,” Nat. Energy, vol. 3, no. 10, p. 828, 2018.
 G. E. Eperon, M. T. Hörantner, and H. J. Snaith, “Metal halide perovskite tandem and multiple-junction photovoltaics,” Nat. Rev. Chem., vol. 1, no. 12, p. 95, 2017.
 “Best Research-Cell Efficiencies, available online. [Accessed: 20 October 2019], 2019.”
 W. Shockley and H. J. Queisser, “Detailed balance limit of efficiency of p‐n junction solar cells,” J. Appl. Phys., vol. 32, no. 3, pp. 510–519, 1961.
 A. De Vos, “Detailed balance limit of the efficiency of tandem solar cells,” J. Phys. D. Appl. Phys., vol. 13, no. 5, p. 839, 1980.
 P. Löper et al., “Organic-inorganic halide perovskite/crystalline silicon four-terminal tandem solar cells,” Phys. Chem. Chem. Phys., vol. 17, no. 3, pp. 1619–1629, 2015.
 C. D. Bailie et al., “Semi-transparent perovskite solar cells for tandems with silicon and CIGS,” Energy Environ. Sci., vol. 8, no. 3, pp. 956–963, 2015.
 J. Zheng et al., “21.8% efficient monolithic perovskite/homo-junction-silicon tandem solar cell on 16 cm2,” ACS Energy Lett., vol. 3, no. 9, pp. 2299–2300, 2018.
 “Imec Perovskite/CIGS tandem cell with Record Efficiency of 24.6 percent Paves the Way for Flexible Solar Cells and High-Efficiency Building-Integrated PV 2018.[Online]. Available:(https://www.imec-int.com/en/articles/perovskite-cigs-tandem- cell-with-rec,” 2018.
 M. Jost et al., “21.6%-Efficient Monolithic Perovskite/Cu (In, Ga) Se2 Tandem Solar Cells with Thin Conformal Hole Transport Layers for Integration on Rough Bottom Cell Surfaces,” ACS Energy Lett., vol. 4, no. 2, pp. 583–590, 2019.
 D. Zhao et al., “Four-terminal all-perovskite tandem solar cells achieving power conversion efficiencies exceeding 23%,” ACS Energy Lett., vol. 3, no. 2, pp. 305–306, 2018.
 S. Albrecht et al., “Monolithic perovskite/silicon-heterojunction tandem solar cells processed at low temperature,” Energy Environ. Sci., vol. 9, no. 1, pp. 81–88, 2016.
 “"PVlighthouse,.” [Online]. Available: https://www.pvlighthouse.com.au/sunsolve.” .
 P. D. Paulson, R. W. Birkmire, and W. N. Shafarman, “Optical characterization of CuIn 1− x Ga x Se 2 alloy thin films by spectroscopic ellipsometry,” J. Appl. Phys., vol. 94, no. 2, pp. 879–888, 2003.
 A. Rajagopal et al., “Highly efficient perovskite–perovskite tandem solar cells reaching 80% of the theoretical limit in photovoltage,” Adv. Mater., vol. 29, no. 34, p. 1702140, 2017.
  Z. Song, C. Chen, C. Li, R. A. Awni, D. Zhao, and Y. Yan, “Wide-bandgap, low-bandgap, and tandem perovskite solar cells,” Semicond. Sci. Technol., vol. 34, no. 9, p. 93001, 2019.
 J. Y. Zhengshan and Z. C. Holman, “Predicting the Efficiency of the Silicon Bottom Cell in a Two-Terminal Tandem Solar Cell,” in 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC), 2017, pp. 3250–3253.
 D. Zhao et al., “Efficient two-terminal all-perovskite tandem solar cells enabled by high-quality low-bandgap absorber layers,” Nat. Energy, vol. 3, no. 12, p. 1093, 2018.
 M. T. Hörantner et al., “The potential of multijunction perovskite solar cells,” ACS Energy Lett., vol. 2, no. 10, pp. 2506–2513, 2017.