Enhanced Charge Transport and Interface Passivation in Efficient Perovskite Solar Cells Using Sulfur-Doped Graphite Carbon Nitride-Modified SnO_2-Based Electron Transport Layers

摘要

High-quality electron transport layer (ETL) is beneficial to improve the chargeextraction and transport, which determines the performance of perovskite solarcells (PSCs). However, the unbalanced charge extraction and interface problemscommonly occur in the tin oxide (SnO_2) ETL. Herein, the sulfur-doped graphitecarbon nitride (CNS) nanosheets are prepared and utilized for modifying theSnO_2 ETL to fabricate high-performance PSCs. The CNS-modified SnO_2 ETLexhibits enhanced electron mobility and conductivity, and matched energy levelwith perovskite, which promotes the extraction and transport of charge carriersat the interface, and balances charge extraction with the hole transport layer.In addition, interfacial carrier recombination is significantly reduced througheffective interface passivation of sulfur atoms in CNS with the undercoordinatedlead ions in perovskite films. Meanwhile, the introduction of an interfacial controlmaterial CNS also contributes to improve the crystalline quality of perovskitefilms with increasing grain size and light absorption intensity. As a consequence,an outstanding improvement in power conversion efficiency (PCE) from 18.98%to 20.33% is achieved after introducing CNS into the SnO_2 ETL, as well as anenhancement in stability against humidity, retaining near 90% of the initial PCEafter aging in the ambient atmosphere for 30 days.