Nature of Photoinduced Quenching Traps in Methylammonium Lead Triiodide Perovskite Revealed by Reversible Photoluminescence Decline

Photoluminescence (PL) of organometal halide perovskite has been broadly investigated as a fundamental signal to understand the photophysics of these materials. Complicated PL behaviors have been reported reflecting complex mechanisms including effects from crystal defects/traps whose nature still remains unclear. Here in this work we observed, besides the PL enhancement, a surprising PL decline phenomenon in methylammonium lead triiodide (CH3NH3PbI3) perovskite showing a high initial PL intensity followed by a fast decline in time scale of milliseconds to seconds. The similarity between the PL enhancement and PL decline suggests both processes are due to PL quenching traps in the material. Combining experimental and theoretical results, two interstitial defects of iodide and lead were identified to be responsible for the PL enhancement and PL decline, respectively. Both traps can be switched between active and inactive states, leading to a reversible process of PL enhancement and PL decline. The identification of the chemical nature of the PL quenching traps is an important step toward fully understanding the crystals defects in these materials.