Phase Variation of Ultrathin WO3 Electron‐Transport Layer Prepared by Scalable Langmuir–Blodgett Technique to Boost Efficiency of Dye Sensitized Solar Cells

Abstract

In third‐generation solar cells, dye sensitized (DSCs) and perovskite (PSCs) both, the role of electron‐transport layers (ETLs) is to block hole transfer at fluorine‐doped tin oxide/mesoporous TiO2 interface, while efficiently transporting the electron at this interface. Conventional solution‐processed dense anatase TiO2 ETL is limited by its low electron mobility. WO3, despite having higher electron mobility and chemical stability, has seldom been used as ETL in DSCs/PSCs, owing to poor crystalline structure and interfacial charge transfer in ETLs prepared using existing methods. Herein this paper, ultrathin and uniform WO3 films of different crystalline structures, such as tetragonal (t‐), orthorhombic (o−), hexagonal (h−), and monoclinic (m−), prepared by scalable Langmuir–Blodgett method, are reported. The efficiency (η) of DSCs fabricated with ETL having high‐symmetry phases of WO3 (h‐WO3, o‐WO3, t‐WO3) is found to exceed the efficiency of devices having ETL of low‐symmetry WO3 phase (m‐WO3). Further, highest η ≈ 9.53%, tantamount to an improvement of 13%, is found in DSCs fabricated with ETL having a mixed phase of o‐ and t‐WO3 and surpassed η of devices based on TiO2 ETLs (8.4%). Herein, the role of structure/phase of WO3 ETLs toward enhancing device performance and outperforming the conventional TiO2 ETLs‐based DSCs is highlighted.