Solar photovoltaics (PVs) are projected to supply up to 79% of global electricity by 2050. The mass production of energy-intensive silicon PV may lead to significant environmental impacts and material demands. Adopting metal halide perovskite tandem PV can further enhance the sustainability of the PV sector due to their potentially higher efficiency yet lower fabrication emissions than silicon PV. Here, we assess the climate and material demand impacts of perovskite tandem deployment on global and regional PV sectors from 2030 to 2050. In addition to the deployment of perovskite tandem into the silicon-dominated PV sector, we consider the fast, slow, and no transitions from perovskite-silicon tandem as a stepping stone to the final all-perovskite tandem PV. The transition can reduce up to 0.43 Mt tin requirement and 16.2% of cumulative carbon emissions from the PV fabrication process. Even without all-perovskite deployment, perovskite-silicon PV can still generate up to a 10.8% cumulative carbon reduction compared to silicon PV scenarios. Besides, the deployment of perovskite tandem systems can reduce energy costs by up to 21.2%, achieving a levelized cost of electricity (LCOE) as low as 3.66 cents/kWh. Achieving these results requires replacing resource-limiting components, such as substituting indium-tin-oxide with fluorinated-tin-oxide analogs.