The hole-blocking and electron-transporting layer is an important component of third-generation solar cells. This layer is responsible for both hindering the hole recombination from the hole-transport layer and collecting photo-generated electrons; that in turn impact photon-to-current conversion efficiency (eta) of devices. Conventionally, WO3 is being used as hole-transport layer owing to high work function and carrier mobility; and excellent thermal stability. In this paper we report ultra-thin WO3 films, prepared by UVO-treatment of WO3-octadecylamine Langmuir-Blodgett multilayers, for use as blocking layers in dye sensitized solar cells (DSSCs). For the first time, it is observed that. of DSSCs with optimized WO3 blocking layer improved significantly (21%) as compared to those based on conventional TiO2 blocking layers. The improvement in. is the result of improved short-circuit current density which is obtained without any accompanying reduction in open-circuit potential and fill factor. This is attributable to the dense and uniform morphology, excellent hole-blocking properties, crystallinity and proper position of Fermi level. The analyses not only reveal that eta of DSSCs can be enhanced by employing ultrathin WO3 LB films as blocking layers but also suggest that the films can possibly be extended further for perosvskite and polymer solar cells. (C) 2019 Elsevier Ltd. All rights reserved.