Interface engineering for efficient and stable back-contact perovskite solar cells

Back-contact perovskite solar cells (BC-PSCs) present a compelling alternative to conventional perovskite architectures by eliminating front-contact electrodes, thus maximizing photon absorption and improving charge collection. However, achieving efficient carrier extraction in BC-PSCs necessitates advanced interface engineering to minimize interfacial defects and optimize charge transport. Here, we introduce an electron transport layer (ETL) by combining nanoparticle SnO₂ with a sol–gel SnO₂ solution, forming a straightforward spin-coating process that enhances interfacial contact, reduces trap-assisted recombination, and improves energy-level alignment. Using conductive atomic force microscopy and photocurrent mapping, we demonstrate that the resulting BC-PSC achieves a maximum power conversion efficiency of 4.52 %, driven by superior charge collection. Additionally, the back-contact configuration enables direct probing of interfacial charge dynamics, providing critical insights into carrier transport mechanisms. These findings highlight the potential of interface-engineered BC-PSCs as a scalable, high-performance platform for next-generation photovoltaics, including flexible and large-area systems.