This study conducts a thorough examination of interface impacts, together with electrical charge movement behavior, at flexible perovskite solar cell (f-PSC) heterojunctions, which use different low-temperature electron transport layers (ETLs). Three different ETLs including \({\text{SnO}}_{2}\) , CdS, and \({\text{T}\text{i}\text{O}}_{2}\) were used to create flexible devices on ITO-coated PET substrates with a \({\text{C}\text{H}}_{3}{\text{NH}}_{3}{\text{PbI}}_{3}\) perovskite absorber and a poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) hole transport layer (HTL). We investigate how different ETL materials affect their surface structures and electrical properties. This then influences the performance of photovoltaic devices. The thin films contain high-quality rutile \({\text{SnO}}_{2}\) and hexagonal CdS and anatase \({\text{T}\text{i}\text{O}}_{2}\) phases together with tetragonal perovskite \({\text{C}\text{H}}_{3}{\text{NH}}_{3}{\text{PbI}}_{3}\) thin films, which show excellent surface coverage and uniform grain distribution and minimal interfacial voids. The \({\text{S}\text{n}\text{O}}_{2}\) -based device with sample A (ITO/PET/ \({\text{SnO}}_{2}\) / \({\text{C}\text{H}}_{3}{\text{NH}}_{3}{\text{PbI}}_{3}\) /PEDOT:PSS/Ag) obtained the highest power conversion efficiency (PCE) of 15.49%, which exceeded the results of CdS-based (11.99%) and \({\text{T}\text{i}\text{O}}_{2}\) -based (9.53%) devices. The \({\text{S}\text{n}\text{O}}_{2}\) -based f-PSC shows better performance because of enhanced interfacial contact and decreased series resistance (8.52 Ω cm2) and elevated shunt resistance (1.961 kΩ cm2), which together minimize recombination losses and leakage current. The Oghma Nano simulator was applied to analyze ideal optical and electrical data, which supported the experimental results. The experimental results validated the simulation outcomes for photon absorption, carrier generation rate, and charge density distribution as \({\text{S}\text{n}\text{O}}_{2}\) outperforms CdS and \({\text{T}\text{i}\text{O}}_{2}\) interfaces in carrier extraction efficiency and built-in potential generation. The combined experimental and simulation results underline the critical role of interfacial engineering in improving the optoelectronic performance and mechanical stability of next-generation flexible photovoltaic devices. The study results deliver essential knowledge for developing affordable high-performance long-lasting flexible perovskite solar cells, which serve portable and wearable energy needs.
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