Mechanism of Photoluminescence Intermittency in Organic−Inorganic Perovskite Nanoparticles
Juan F. Galisteo-López a, Mauricio E. Calvo a, Cristina T. Rojas a, Hernán Míguez a
a Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Cientίficas, c/ Américo Vespucio 49, Sevilla, 41092
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Oral, Juan F. Galisteo-López, presentation 162
Publication date: 11th February 2019

Reducing the dimensions of lead halide perovskites down to the nanoparticle (NP) level can further expand the acknowledged potential of this material for optoelectronic applications. One example is their use in light emitting devices as a promising route to improve their performance. [1] A limitation of these NP is the presence of photoluminescence (PL) intermittency which lowers its quantum efficiency and could compromise its applicability. Such PL blinking has been observed in lead halide perovskites of different nature and morphology and its precise origin has not yet been clarified.

In this work we have studied the PL temporal evolution of crystalline CH3NH3PbBr3 NPs having an average size of 40nm, well above the Bohr’s exciton radius for this material and thus far from the quantum confinement regime. The NPs present a PL which oscillates between different intensity levels when illuminated over a period of several minutes under continuous wave illumination. Contrary to inorganic quantum dots where such intermittency takes place as a sucesion of on/off states, multiple PL levels are observed for the perovsktie NPs.

In order to understand such PL intermittency we have exposed the NPs to different atmospheres. We find that the PL intermittency remains upon changes in the surrounding atmosphere though the higher and lower PL levels dominate when the NPs are exposed to O2 and N2 respectively. Based on these findings and previous ones dealing with the emission of the bulk material [2] we propose a mechanism for the PL intermittency in which an interplay between photoinduced trap creation/annihilation takes place as a consequence of the interaction between the photoexcited NP and the atmosphere. [3] 

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