An annealing-free anatase TiO2 nanocrystal film as an electron collection layer in organic solar cells

Abstract

Anatase TiO₂ film, which is traditionally fabricated by high-temperature annealing of TiO_x precursors, has been widely used as an electron collection layer in photovoltaics. In order to avoid the undesired high temperature treatment, in this work, we developed a convenient and moderate procedure to fabricate anatase TiO₂ nanocrystal films at room temperature. Ultrafine, clean and high-quality anatase TiO₂ nanocrystals have been pre-prepared in a simple solvothermal route and subsequent spin-coating of the nanocrystal dispersion provides a well formed TiO₂ nanocrystal film without any further thermal treatment. The characteristics of the TiO₂ nanocrystal film, in terms of crystallization phase, film morphology, optical and electronic properties, have been carefully studied, and then a typical [ITO/TiO₂/P3HT:PCBM/MoO₃/Ag] inverted photovoltaic device using TiO₂ nanocrystals as the ECL has been fabricated and exhibits a comparable power conversion efficiency (PCE) of 3.35% to that of the conventional device (3.39% PCE).