Age-induced recrystallization in perovskite solar cells

Organic-inorganic hybrid perovskite with single or multiple ions is extensively investigated as light-harvesting material in fabricating high-efficiency photovoltaic cells. There is much less effort into the understanding of the structure and electronic properties than into device optimization. The highest efficiency usually appears some time (a couple of days) after the device fabrication, but the underlying mechanism is rarely in the limelight. Here we study device performance under different storage environments. We utilize X-ray diffraction, time-resolved photoluminescence, transient absorption spectrometer, and single-carrier diode measurement to understand the structure and electronic properties of perovskite films for the time scale of weeks. We observe enhanced crystallinity and crystallite size, referred to age-induced recrystallization. Based on the structural changes, the charge trap and recombination are suppressed, while charge transport and collection are enhanced, ultimately improving device efficiency.