Annealing free CeO2 electron transport layer for efficient perovskite solar cells

Electron transport material plays a critical role in perovskite solar cells. The most commonly used electron transport material, TiO2, has to be sintered at high temperature to achieve good crystallinity and high carrier mobility, complicating the preparation procedure and limiting the development of flexible devices. In this work, we firstly propose a kind of stoichiometric CeO2 film as annealing free electron transport layer for efficient perovskite solar cells. The CeO2 nanocrystals are prepared by solvothermal method. The obtained CeO2 nano -crystals can be well re-dispersed in cyclohexane to form a stable, homogeneous and transparent solution. As a result, we can prepare the CeO2 electron transport layer by spin-coating method and without any annealing or drying process. The performance of the CeO2 electron transport layer is regulated by optimizing the solvothermal reaction time. It is found that the CeO2 nanocrystals prepared under 48 h display the most excellent electron extraction performance. The corresponding device acquires a power conversion efficiency of 13.69%. The effi-ciency is further improved to 16.53% after introducing C60 interlayer. The work presents that CeO2 can be an efficient low temperature processed electron transport material for perovskite solar cells.