The ionic defects of hetero-junction interfaces always attract and trap carriers via surface electrostatic forces, which are crucial for the efficiency and intrinsic stability of perovskite solar cells (PSCs). Herein, functionalized carbon nanotubes (CNTs) have been utilised to chemically link the SnO2/perovskite interface affecting both the trap states and energy levels. Theory and experiments indicate that the CNTs act as electron donors to SnO2, and the Pb-cluster based perovskite, which results in n-type doping of SnO2 and shifts the 6p-orbitals of the Pb-cluster to the conduction band (CB) edge, converts the deep trap states to the shallower one. By using the interface linker, the power conversion efficiency (PCE) of PSC devices yields 24.04% with a high fill factor of 83%. In addition, the PSCs have better operational and thermal stability and we demonstrate that after 1000 h under 1 sun illumination at 65 & DEG;C heating the device retains 88.15% of the initial efficiency.