Compact TiO₂/Anatase TiO₂ Single-Crystalline Nanoparticle Electron-Transport Bilayer for Efficient Planar Perovskite Solar Cells

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Electron-transport layer (ETL)/perovskite interface modification plays a key task for producing efficient planar perovskite solar cells (PSCs). In this study, interfacial modification of compact TiO 2 using novel, one-step hydrothermally synthesized single-crystalline anatase (AT) titania nanoparticles (TiO 2 NPs) (average diameter = 6–10 nm) was applied as an ETL bilayer to enhance the efficient charge generation and extraction and eliminate the electron–hole recombination ratio. We report here an easy approach for enhancing the performance of planar PSCs by introducing a compact TiO 2 /AT TiO 2 NPs bilayer through spray pyrolysis (SP) deposition and spin-coating (SC) techniques, respectively. The enhanced performance of the devices with an SP-TiO 2 /SC-AT TiO 2 NPs bilayer facilitated more efficient electron transport, charge extraction, and low interfacial recombination. Ultimately, the best device had a 17.05% power conversion efficiency resulting from the significant decrease in J–V hysteresis, presenting almost a 12% performance improvement compared to the TiO 2 only layer-based counterpart. Thus, the present study provides an important advance to the design of photovoltaic devices with respect to charge transport and electron–hole recombination.