The study explores the simplification of perovskite solar cells (PSCs) by replacing the mesoporous electron selective layer (ESL) with a planar one, specifically using TiO2 and SnO2. Planar PSCs with TiO2 ESLs exhibit unstabilized power conversion efficiencies (PCEs) due to conduction band misalignment. In contrast, SnO2, with its deeper conduction band, achieves barrier-free energetic configuration, resulting in PCEs of over 18% and record-high voltages of up to 1.19 V. The research highlights the importance of correct band alignment for high efficiency and stability in planar PSCs, demonstrating that SnO2-based devices show improved charge extraction and hysteretic behavior compared to TiO2-based devices. Femtosecond transient absorption measurements confirm the better electron injection dynamics in SnO2, supporting the hypothesis of barrier-free charge transport across the perovskite/SnO2 interface.The study explores the simplification of perovskite solar cells (PSCs) by replacing the mesoporous electron selective layer (ESL) with a planar one, specifically using TiO2 and SnO2. Planar PSCs with TiO2 ESLs exhibit unstabilized power conversion efficiencies (PCEs) due to conduction band misalignment. In contrast, SnO2, with its deeper conduction band, achieves barrier-free energetic configuration, resulting in PCEs of over 18% and record-high voltages of up to 1.19 V. The research highlights the importance of correct band alignment for high efficiency and stability in planar PSCs, demonstrating that SnO2-based devices show improved charge extraction and hysteretic behavior compared to TiO2-based devices. Femtosecond transient absorption measurements confirm the better electron injection dynamics in SnO2, supporting the hypothesis of barrier-free charge transport across the perovskite/SnO2 interface.