Vacuum thermal-evaporated SnO2 as uniform electron transport layer and novel management of perovskite intermediates for efficient and stable planar perovskite solar cells

Abstract

Abstract Tin oxide (SnO2) has been confirmed as a vital electron transport material for efficient planar perovskite solar cells (PSCs) owing to its outstanding electrical and optical properties. Defectively, the SnO2 electron transport layer (ETL) by spin coating still remains great challenges for repeatable planar heterojunction PSCs fabrication for its limited scale and incompetent uniformity. Herein, the vacuum thermal-evaporation procedure is employed to achieve this intent by the dense and uniform SnO2 layer, which can largely improve the material utilization for cost reduction and act as a potential for the prospective industrial large-scale fabrication. Besides, a post-annealing treatment of evaporated SnO2 is proved obbligato to achieve an ideal crystallinity improvement. Furthermore, to remove the antisolvent method for perovskite, methyl ammonium acetate (MAAc) worked as an additive into the perovskite precursor for a pure MAPbI3 film to achieve the poisonous antisolvent free. Noticeable, the formation of an unstable MAPbI3-xAcx intermediate certainly has a great impact on the resulting perovskite, in which the particular surface-morphology was dominated by the MAAc volatilization rate. The obtained morphology with fluctuant pits and ridges, like a 3D-structure, contributes to more light absorption and contact area at perovskite/charge transport material interface, leading to higher photocurrent, more efficient charge extraction and better device performance. As a result, an optimal cell device can remain 86% of its initial photovoltaic performance (PCE: 16.79%) after a 50-d storage in air.