Room-temperature sputtered-SnO2 modified anode toward efficient TiO2-based planar perovskite solar cells

Abstract

It is of the utmost importance to promote the charge transport and retard the heterojunction barrier in the functional layers and at their adjacent interfaces to pursuit excellent photovoltaic characteristics of the perovskite solar cells (PSCs). Here, room-temperature sputtered-SnO2 films are introduced to modify FTO anode for improving carrier extraction and aligning energy band in the TiO2-based planar PSCs. For the SnO2-modified substrate with suitable sputtering duration, the following TiO2 film exhibits smoother surface roughness, less surface defects, and lower the trap-assisted interfacial recombination than that directly on the FTO, further facilitating the growth of perovskite grain size and promoting the extraction efficiency of charge carriers. On the basis of the optimized SnO2(6 nm)/TiO2 stack layer as electron transport layer (ETL), the PSC exhibits an outstanding power conversion efficiency of 21.45%, which is much better than that of the single TiO2-based device (19.68%). More importantly, the cell with the bilayer ETL shows a long-term stability against air, maintaining over 76% of its initial efficiency after 40 d. These achievements suggest that this study provides a feasible path to design energy level alignment and low temperature ETL for highly efficient and stable PSCs.