Tin dioxide -(SnO2) has been demonstrated as one of the promising electron transport layers for highefficiency perovskite solar cells (PSCs). However, scalable fabrication of -SnO2 films with uniform coverage, desirable thickness and a low defect density in perovskite solar modules (PSMs) is still challenging. Here, we report preparation of high-quality large-area -SnO2 films by chemical bath deposition (CBD) with the addition of -KMnO4. The strong oxidizing nature of -KMnO4 promotes the conversion from Sn(II) to Sn(VI), leading to reduced trap defects and a higher carrier mobility of -SnO2. In addition, K ions diffuse into the perovskite film resulting in larger grain sizes, passivated grain boundaries, and reduced hysteresis of PSCs. Furthermore,Mn ion doping improves both the crystallinity and the phase stability of the perovskite film. Such a multifunctional interface engineering strategy enabled us to achieve a power conversion efficiency (PCE) of 21.70％ with less hysteresis for lab-scale PSCs. Using this method, we also fabricated 5 × 5 and 10 × 10 -cm2 PSMs, which showed PCEs of 15.62％ and 11.80％ (active area PCEs are 17.26％ and 13.72％), respectively. For the encapsulated 5 × 5 -cm2 PSM, we obtained a -T80 operation lifetime (the lifespan during which the solar module PCE drops to 80％ of its initial value) exceeding 1000 h in ambient condition.