Facile Surface Engineering of Composite Electron Transport Layer for Highly Efficient Perovskite Solar Cells with a Fill Factor Exceeding 81%

Abstract

After perovskite became a star material, research on perovskite solar cells (PSCs) became a hot topic and developed rapidly. Electron transport layers (ETLs) with high mobility, low‐defect state, and suitable energy level arrangement dominate the development of planar heterojunction PSCs. In this work, the K+ and Cs+ doped composite SnO2 ETL (x mg KC‐SnO2) by a continuous spin‐coating of the x mg Cs+@KOH and SnO2 aqueous solution shows a substantial improvement in carries extraction, transport and collection properties, leading to the increased fill factor (FF) from 72.48% to 81.00% of the planar heterojunction PSCs, and finally the champion device average efficiency is 21.62%. Moreover, this work improves the interface contacts between ETL/Perovskite, as it reduces energy disorder and simultaneously promotes electron transport, charge extraction at the interface, improve energy level alignment and quasi‐Fermi level splitting, and decreased resistance for charge transfer in the device. In conclusion, this simple and effective method of improving the FF value provides a certain shortcut to the performance of plane heterogeneous perovskite devices.

Recent Progress in Perovskite Solar Cells: Status and Future

“…The PM-treated PSC had a PCE of up to 22.93%, with negligible hysteresis. Zong et al used continuous spin coating to fabricate SnO 2 @K:Cs [86] and SnO 2 @Na:Cs ETLs [87], respectively. The better PCE was 22.06%, based on a SnO 2 @Na:Cs ETL.…”

Enhanced Perovskite Solar Cell Stability and Efficiency via Multi‐Functional Quaternary Ammonium Bromide Passivation

“…The method of low-dimensional perovskite passivation 3D perovskite has positive effect of improving the efficiency and stability of PSCs. [25][26][27][28][29][30][31] Even though the quality of the perovskite films were optimized by the reported effective passivation methods, but most of the optimization are conducted by single functional, and the optimized perovskite still suffers from the corrosion of the external environment (such as high humidity) directly. Therefore, it's time to develop suitable passivators with functional groups which not only for passivated defects, but also need external protective functional groups for resistance to environmentalThe Achilles heel of the perovskite solar cells (PSCs) is the long-term stability under working condition which restricts the commercialization.…”

“…[25] Wang et al evidenced that BA + can form a two-dimensional (2D) layered perovskite with a wide band gap upon the threedimensional (3D) perovskite. [28] When migrating to the grain boundaries in the 3D perovskite layer, the carriers are blocked by the 2D/3D heterojunction and continue to propagate in the crystal grains rather than by recombination. The method of low-dimensional perovskite passivation 3D perovskite has positive effect of improving the efficiency and stability of PSCs.…”