Enhanced Efficiency and stability of Perovskite Solar Cells using Porous Hierarchical TiO₂ Nanostructures of Scattered Distribution as Scaffold

A type of quasi-mesoscopic perovskite solar cells (QM-PSCs) with porous hierarchical TiO₂ (hier-TiO₂) nanostructures of scattered distribution as scaffold was investigated. The porous hier-TiO₂ nanostructures were synthesized by sintering MIL-125(Ti) of metal-organic frameworks (MOFs) at 500 °C in air and which were partly inherited from the ordered porosity of MIL-125(Ti). The ordered hier-TiO₂ nanostructures were scattered on compact TiO₂ layer to form a quasi-mesoscopic scaffold of scattered distribution, which can offer enough growth space for perovskite grains and promote the ordered growth of perovskite grains. The QM-PSCs shows a power conversion efficiency (PCE) of 16.56%, much higher than PCE (11.38%) of PSCs with conventional small TiO₂ nanoparticles (npt-TiO₂) as scaffold and PCE (6.07%) of planar PSCs with compact TiO₂ layer. The PCEs of PSCs with hier-TiO₂ and npt-TiO₂ remain 47% and 22% of the initial PCE values aging for 30 days in air, indicating that PSCs with hier-TiO₂ scaffold shown better stability and moisture resistance. The enhanced performance of QM-PSCs is primarily attributed to the superior wettability quasi-mesoscopic scaffold with ordered porous hier-TiO₂ nanostructures, which help to form the high quality perovskite film with better crystillinity and less pin-holes, and improve the contact properties between perovksite and electron transport layer.