Facile fabrication of large grain CH3NH3PbI3 xBrx films for high efficiency solar cells via CH3NH3Br selective Ostwald ripening
Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low cost, high efficiency photovoltaic technology. Structural and electro optical properties of the perovskite absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high efficiency PSCs based on compact, large grain, pinhole free CH3NH3PbI3 xBrx (MAPbI3 xBrx) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin coating with a proper MABr concentration converts MAPbI3 thin films with different initial film qualities (for example, grain size and pinholes) to high quality MAPbI3 xBrx thin films following an Ostwald ripening process, which is strongly affected by MABr concentration and is ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I Br anion exchange reaction, yielding poorer device performance. This MABr selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability.
Nature communications