This study presents a method to achieve highly efficient planar perovskite solar cells (PSCs) by optimizing band alignment engineering. The research demonstrates that replacing the traditional mesoporous electron selective layer (ESL) with a planar one improves scalability and manufacturing. The study shows that planar PSCs using TiO₂ as the ESL are limited by conduction band misalignment, while SnO₂ achieves a barrier-free energetic configuration, resulting in almost hysteresis-free PCEs of over 18% with record high voltages of up to 1.19 V. The key finding is that SnO₂ provides a better alignment of the conduction bands, enabling efficient charge extraction and long-term air stability. The study also shows that the use of SnO₂ allows for low-temperature processing, which is crucial for scaling up production and creating high-efficiency tandem devices. The research highlights the importance of proper band alignment for efficient PSCs, especially in planar devices with compact charge selective layers. The study also demonstrates that the use of SnO₂ leads to improved charge transport and reduced hysteresis compared to TiO₂. The results show that SnO₂-based PSCs have higher power conversion efficiencies and better stability than TiO₂-based devices. The study also shows that the use of SnO₂ allows for higher voltages and better performance in PSCs. The research provides a clear understanding of the role of band alignment in PSC performance and highlights the potential of SnO₂ as a promising ESL for high-performance PSCs.This study presents a method to achieve highly efficient planar perovskite solar cells (PSCs) by optimizing band alignment engineering. The research demonstrates that replacing the traditional mesoporous electron selective layer (ESL) with a planar one improves scalability and manufacturing. The study shows that planar PSCs using TiO₂ as the ESL are limited by conduction band misalignment, while SnO₂ achieves a barrier-free energetic configuration, resulting in almost hysteresis-free PCEs of over 18% with record high voltages of up to 1.19 V. The key finding is that SnO₂ provides a better alignment of the conduction bands, enabling efficient charge extraction and long-term air stability. The study also shows that the use of SnO₂ allows for low-temperature processing, which is crucial for scaling up production and creating high-efficiency tandem devices. The research highlights the importance of proper band alignment for efficient PSCs, especially in planar devices with compact charge selective layers. The study also demonstrates that the use of SnO₂ leads to improved charge transport and reduced hysteresis compared to TiO₂. The results show that SnO₂-based PSCs have higher power conversion efficiencies and better stability than TiO₂-based devices. The study also shows that the use of SnO₂ allows for higher voltages and better performance in PSCs. The research provides a clear understanding of the role of band alignment in PSC performance and highlights the potential of SnO₂ as a promising ESL for high-performance PSCs.