Due to unprecedented optoelectronic properties and a rapid increase in power conversion efficiency (PCE) in just a decade perovskite solar cells (PSCs) came under the limelight in the field of photovoltaics (PVs). [1][2][3] So far, the efficiency of single-junction PSCs has reached 25.7%, which is at par with state-of-the-art crystalline silicon solar cells (SCs). [4][5][6][7] In contrast to singlejunction PVs, tandem solar cells (TSCs) is more promising route to acquire higher PCE. [8] By integrating semiconductor lightabsorbing materials (with different bandgaps in a PV device) can be able to absorb photons in different wavelength to the maximum extent. Consequently, sunshine is best utilized and the optical loss of the SC can be minimized. [9][10][11] The technique of using distinguished bandgap semiconducting materials in multi-junction devices resulted in exceeding the efficiency to 38% which is much more than that of singlejunction devices, which are reported to be only 29% efficient. [7] However, this advantage of semiconductor materials came up with a price of expensive materials and complicated fabrication processes. [8,11] Numerous advantages of perovskite materials, for example, their outstanding PV performance, low price, and effortless fabrication process, etc., rushed the scientific community to use them in tandem devices. [12,13] The efficiency of perovskite-silicon TSCs has reached 31.3%, which is a great breakthrough but still its commercialization is facing hampering due to flexibility, weight, and cost due to their rigid counterparts. [7,13] Contrastingly, all-perovskite TSCs have a significant place in the fast development of perovskite PVs because of their synergistic advantage of low-cost solution processing and high-efficiency prospects. [14][15][16][17] The highest demonstrated efficiency of all-perovskite TSCs to date is 26.4%. [7,18,19] Although its little far from the efficiency of perovskite-silicon TSCs still, it has a broader room for the development of flexible device fabrication. [20][21][22] Lightweight flexible SCs are more cost-effective for transport, storage, and installation. Their flexibility making them ideal for building/vehicle-integrated PVs, wearable electronics, power supplies for flexible skin, portable energy systems, and aerospace applications. [23][24][25] In recent years, scientists have developed a strong interest in the study of flexible single-junction perovskite SCs. [26][27][28][29][30] In just 9 years, the efficiency of flexible perovskite SCs has increased dramatically (from 2.6% to 23.6%). [7,31] However, this efficiency is still far from the certified efficiency of 25.7% compared with single-junction rigid PSCs. [5] Designing flexible all-perovskite TSCs with different bandgaps is one of the most effective ways to increase the efficiency limit of single-junction flexible PSCs. [10,20] The PV community centered their focus to