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HIGHLIGHTS• Nanoscale multi-dimensional heterojunctions in situ grow at the edge of two-dimensional MXene conductive network.• A controlled anneal procedure in 150 °C is for preparing anatase TiO 2 /SnO 2 heterojunctions with oxygen vacancy scramble effect.• The perovskite solar cells achieve high power conversion efficiency and high moisture-resistance stability.ABSTRACT A multi-dimensional conductive heterojunction structure, composited by TiO 2 , SnO 2 , and Ti 3 C 2 T X MXene, is facilely designed and applied as electron transport layer in efficient and stable planar perovskite solar cells.Based on an oxygen vacancy scramble effect, the zero-dimensional anatase TiO 2 quantum dots, surrounding on two-dimensional conductive Ti 3 C 2 T X sheets, are in situ rooted on three-dimensional SnO 2 nanoparticles, constructing nanoscale TiO 2 /SnO 2 heterojunctions. The fabrication is implemented in a controlled lowtemperature anneal method in air and then in N 2 atmospheres. With the optimal MXene content, the optical property, the crystallinity of perovskite layer, and internal interfaces are all facilitated, contributing more amount of carrier with effective and rapid transferring in device. The champion power conversion efficiency of resultant perovskite solar cells achieves 19.14%, yet that of counterpart is just 16.83%. In addition, it can also maintain almost 85% of its initial performance for more than 45 days in 30-40% humidity air; comparatively, the counterpart declines to just below 75% of its initial performance.