Room-temperature preparation of crystalline TiO<inf>2</inf> thin films and their applications in polymer/TiO<inf>2</inf> hybrid optoelectronic devices

Highly homogeneous crystalline TiO2 thin films with very low surface roughness were prepared by spin-coating of a TiO2 nanoparticle aqueous dispersion at room temperature without further heat treatment. Using these films as electron transporting layers, inverted structure hybrid photovoltaic cells (TiO2/P3HT) and light-emitting diodes (TiO2/F8BT) were demonstrated. The photovoltaic cells exhibited an energy conversion efficiency of 0.26%, which is similar to that of cells utilizing TiO2 layers sintered at high temperatures. Moreover, the light-emitting diodes showed an efficiency of 0.65 cd/A, which is higher than obtained from a reference inverted diode (0.1 cd/A). These measurements demonstrate that a properly designed nanoparticle casting route can help avoid high temperature crystallization or sintering steps for TiO2 thin films, paving the road for their use in conjunction with plastic substrates. © 2011 Elsevier B.V. All rights reserved