Flocculating-Regulated TiO2 Deposition Enables the Synergistic Effect of Doping for Perovskite Solar Cells with Efficiency Exceeding 25.8%

Abstract

The planar perovskite solar cells (PSCs) using TiO₂ as the electron transport layer (ETL) are undergoing a stagnated efficiency improvement, which the inferior TiO₂ ETL mainly limits. Herein, a flocculating-regulated TiO₂ deposition using SnCl₂·2H₂O is reported as the flocculate to control the nanoparticle size finely for optimizing TiO₂ deposition and to achieve a synergistic Sn doping. The SnCl₂·2H₂O incorporated into bath precursor can bridge-link the suspended nanoparticles, which promotes the precipitation of large-sized nanoparticles and leaves the smaller-sized nanoparticles for deposition, leading to a compact TiO₂ film with marked reduced surface roughness. Meanwhile, along with flocculating-regulated TiO₂ deposition, it can also be achieved the Sn-doping of TiO₂, which increases the conductivity of TiO₂ thin films by ≈2.5 times. As a consequence, attributing to the optimized interface contact and accelerated interfacial electron transport, the planar PSCs achieved a certification efficiency of 25.85%, the highest value among the TiO₂-based planar PSCs to date. In addition, the PSCs can maintain 99% of their initial efficiency after more than 4500 h of storage in ambient air, showing excellent stability.