Tandem solar cells have spurred much interest among the researchers because they provide an efficient way to harvest an extensive spectrum of solar emission by integrating two or more subcells with varying bandgap. However, the understanding related to working phenomenon of the interfacial layer integrating the absorption layers in a tandem solar cell lags and these interlayer plays a significant role in achieving higher efficiency. In this manuscript, we inquire the aspect of the p-type and n-type conducting region creating an interlayer and several significant factors of the tandem cell-like interfacial engineering, optical optimisation and incident photon to current efficiency and PCE characteristics. Closer investigation of the interlayer, consisting of the n-type nanocrystalline semiconductor materials like TiO2/ZnO/SnO2 and a p-type hole mobility layer explains the ohmic contact phenomenon through the metal/semiconductor interface. Here, we determine that a higher efficiency tandem solar cells with a power conversion efficiency of about 8.2% can be attained through an effective interlayer attribute and different absorption bands for electron generation. The understanding experienced in this manuscript can be constructive in enhancing the efficiency of the tandem solar cells further with wider bandgap polymers. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.